I get a 0 on white screen on the front end when booking an appointment.

Hi,
Please help, I keep getting a 0 (zero) on a white screen when I try to book an appointment. This use to work perfectly. I have tried everything.

1) I uninstalled and reinstalled the plugin
2) I changed themes
3) I Deactivated other plugins
4) I ran a Wp Sweep and tried deleting the remaining tables left after uninstall
What am I missing? I never found the tables to delete.
5) I also updated my PHP to php73.

IMPORTANT! When I reinstall the salon plugin, all the old settings remain saved and I don’t know why if I deleted all folders from the FTP?
If I can somehow completely remove the plugin maybe it will install fresh and correctly. Please HELP!