I was able to upload the game, this time via MakeCode. There have been so many times when it hasn’t worked, but now it is working.
I have exactly the same bootloader version:
UF2 Bootloader v3.10.0 SFHWRO
Model: PyGamer
Board-ID: SAMD51J19A-PyGamer-M4
I suspect that either something is wrong with my computer, or USB cable, or my browser (i’ve used Microsoft Edge and Chrome), or maybe the capacity of the device:
The PyGamer is powered by our favorite chip, the ATSAMD51, with 512KB of flash and 192KB of RAM. We add 8 MB of QSPI flash for file storage, handy for images, fonts, sounds, or game assets.
@richard
Do know if there is a limitation of how big Arcade games can be when uploading to a adafruit PYGAMER? The version I was eventually able to upload is 708KB.