From the U.S. Postal Service announcement on November 17, 2020:
From the USPS: This Happy Birthday stamp conveys exuberant greetings by calling to mind the childhood excitement of a birthday party. Each of the five letters in the word “HAPPY” is inspired by a different party decoration in the midst of a flurry of multicolored ribbons and confetti. This stamp was designed by Lisa Catalone Castro and Rodolfo Castro, featuring a digital illustration by the latter. Ethel Kessler served as art director.
This stamp will be issued September 9th in Toast, N.C., but without a first-day ceremony.
The Scott catalogue number for this issue is 5635.
Additional information will be posted below the line, with the most recent at the top.
Updated August 25th:
Here are the first-day postmarks for this issue:
The Digital Color Postmark measures 2.54″ x 1.45″ 
The pictorial postmark measures 2.39″ x 1.15″
Updated July 30th from the Postal Bulletin:
On September 9, 2021, in Toast, NC, the United States Postal Service® will issue the Happy Birthday stamp (Forever® priced at the First-Class Mail® rate) in one design, in a pressure-sensitive adhesive (PSA) pane of 20 stamps (Item 577700). This stamp will go on sale nationwide September 9, 2021, and must not be sold or canceled before the first-day-of-issue.
This Happy Birthday stamp conveys exuberant greetings by calling to mind the childhood excitement of a birthday party. Each of the five letters in the word “HAPPY” is inspired by a different party decoration in the midst of a flurry of multicolored ribbons and confetti. Featuring a digital illustration by Rodolfo Castro, this stamp was designed by Lisa Catalone Castro and Rodolfo Castro. Ethel Kessler served as art director.
No automatic distribution.
How to Order the First-Day-of-Issue Postmark:
Customers have 120 days to obtain the first-day-of-issue postmark by mail. They may purchase new stamps at their local Post Office™ or at The Postal Store® website at usps.com/shop. They must affix the stamps to envelopes of their choice, address the envelopes (to themselves or others), and place them in a larger envelope addressed to:
FDOI – Happy Birthday Stamp
USPS Stamp Fulfillment Services
8300 NE Underground Drive, Suite 300
Kansas City, MO 64144-9900
After applying the first-day-of-issue postmark, the Postal Service™ will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. There is a 5-cent charge for each additional postmark over 50. All orders must be postmarked by January 9, 2022.
Technical Specifications:
Issue: Happy Birthday Stamp
Item Number: 577700
Denomination & Type of Issue: First-Class Mail Forever
Format: Pane of 20 (1 design)
Series: N/A
Issue Date & City: September 9, 2021, Toast, NC 27049
Art Director: Ethel Kessler, Bethesda, MD
Designer: Lisa Catalone Castro, Bethesda, MD
Designer: Rodolfo Castro, Bethesda, MD
Illustrator: Rodolfo Castro, Bethesda, MD
Modeler: Joseph Sheeran
Manufacturing Process: Offset, Microprint
Printer: Ashton Potter (USA) Ltd. (APU)
Press Type: Muller A76
Stamps per Pane: 20
Print Quantity: 50,000,000 stamps
Paper Type: Nonphosphored Type III, Block Tag
Adhesive Type: Pressure-sensitive
Colors: Black, Cyan, Magenta, Yellow
Stamp Orientation: Horizontal
Image Area (w x h): 1.05 x 0.77 in. / 26.67 x 19.558 mm
Overall Size (w x h): 1.19 x 0.91 in. / 30.226 x 23.114 mm
Full Pane Size (w x h): 5.76 x 5.55 in. / 146.304 x 140.97 mm
Plate Size: 320 stamps per revolution
Plate Number: “P” followed by four (4) single digits in four corners
Marginal Markings:
Front: Plate number in four corners
Back: ©2020 USPS • USPS logo • Two barcodes (577700) • Plate position diagram (8) • Promotional text
From the USPS: America’s love of coffee is celebrated with four new stamps in a booklet of 20. Four digital illustrations feature cups of four different drinks: caffe latte, espresso, caffe mocha and cappuccino. The names of the espresso drinks appear in art-deco-inspired lettering above or below each cup. Art director Greg Breeding designed the stamps with original artwork by Terry Allen.
From the USPS: This stamp celebrates the bicentennial of Missouri statehood. Missouri became the 24th state in the Union on Aug. 10, 1821. The stamp art is an existing photograph of Bollinger Mill State Historic Site by noted landscape photographer Charles Gurche. Art director Greg Breeding designed the stamp.
From the USPS: The long-running series celebrating American lighthouses continues with five new stamps. The mid-Atlantic lighthouses featured in this issuance are: Thomas Point Shoal, MD; Montauk Point, NY; Harbor of Refuge, DE; Navesink, NJ; and Erie Harbor Pierhead, PA. The late Howard Koslow 
From the USPS: The U.S. Postal Service celebrates the enduring legacy of Western wear with four fun new Forever stamps in a booklet of 20. The stamp art features four graphic illustrations of Western wear staples — a cowboy hat, a cowboy boot with a spur, a Western shirt, and a belt buckle featuring a longhorn head. Each image is framed by elements common to the American West and iconography of the region, including cacti, snakes, roses and stars. Art director Greg Breeding designed the stamps with original art by Ryan Feerer.
From the USPS: With this commemorative stamp, the Postal Service recognizes the contributions of Japanese American soldiers, some 33,000 altogether, who served in the U.S. Army during World War II. The stamp, printed in the intaglio method, is based on a photograph. “Go for Broke” was the motto of the all-Japanese American 100th Infantry Battalion/442nd Regimental Combat Team and came to represent all Japanese American units formed during World War II. The stamp was designed by art director Antonio Alcalá.
From the USPS: Merging traditional artwork with modern design touches, this stamp depicts one of many stories about Raven, a figure of great significance to the Indigenous peoples of the Northwest Coast. Among the cultures of the region, Raven plays an essential role in many traditional tales, including stories about the creation of the world. Inspired by the traditional story of Raven setting free the sun, the moon and the stars, Tlingit/Athabascan artist Rico Worl depicts Raven just as he escapes from his human family and begins to transform back into his bird form. Antonio Alcalá served as art director.
From the USPS: These stamps pay tribute to heritage breeds, preindustrial farm animals that are enjoying renewed attention for their versatility, adaptability and unique genetic traits. This pane of 20 stamps includes photographs of 10 heritage breeds: the American Mammoth Jackstock donkey, the Narragansett turkey, the Cayuga duck, the San Clemente Island goat, the Mulefoot hog, the Cotton Patch goose, the American Cream draft horse, the Barbados Blackbelly sheep, the Milking Devon cow and the Wyandotte chicken. Zack Bryant designed the stamps with photographs by Aliza Eliazarov. Greg Breeding served as art director.
Just a guess: The Accocreek Post Office may not have the staff or experience to handle a first-day.
From the USPS: The Postal Service features a brush rabbit (Sylvilagus bachmani) on this beautiful new additional-ounce stamp, available on a pane of 20 or in a coil of 100. The pencil-and-watercolor illustration is from preexisting artwork by designer and illustrator Dugald Stermer. The brush rabbit is a small brownish cottontail rabbit of the U.S. West Coast and Baja California, Mexico. Art director Ethel Kessler designed the stamp.
Brush Rabbit stamp (Non-denominated Additional Ounce Rate) in one design, in a pressure-sensitive adhesive (PSA) pane of 20 stamps (Item 121100) and a PSA coil of 100 stamps (Item 740300). This stamp will go on sale nationwide January 24, 2021, and must not be sold or canceled before the first-day-of-issue.
