I notice you are running umbrelOS 0.5.4, one of the the first suggestions I can make that might help is to update to a more recent version of umbrelOS.
Otherwise could you try what this comment suggested fir a similar issue? BTCPAY won't start after install - #2 by usernameisJim
Failing that, could you post the full logs of BTCPayServer? I’m not sure how to get it on your version but on newer versions of umbrelOS it’s Settings > Troubleshoot > App > BTCPayServer