If the app does not start at all, there are several things you can check:
Make sure that you are running macOS version 10.15 or above
Check if you have the newest version of o/PHANTOMFUSE installed - Uninstall and reinstall
If that doesn't help, please run o/PHANTOMFUSE from the Terminal app with this command and send us the output:
/Applications/PHANTOMfuse/PHANTOMfuse.app/Contents/MacOS/PHANTOMfuse