Firstly, apologies for taking so long to respond. Secondly, thanks a billion for buying the demo, I hope it lives up to expectations!
In regards to the loading issues, is your pico8 updated to the latest version? Theres a few functions Umbra uses that dont work with older versions of pico8.
If you're updated, how are you loading the carts into pico8?
Again, thank you for buying the demo, lmk if you have any other issues.