Your app seems to be in a “detached” state - this is a sort of halfway-migrated state that should only happen while an app is being migrated.
Fixing this shouldn’t be that bad. You should be able to run
fly resume <appname> # to get out of the "suspended" state
fly scale count 0 -a <appname> # to kill any leftover VMs from the old platform, if there are any
# scale count 0 might take a minute to propagate in the backend.
# if the next command fails, try it again after a few seconds.
fly apps set-platform-version machines -a <appname>
This should get your app in a normal state.