there is new version of EasyAppointments 3.8.1 with updated dependencies to avoid conflict with Events Tickets plugin.
Please use only 3.8.1, there was some issues with 3.8.0 that can break update process.
Issue was missing file `vendor/composer/platform_check.php` that was left out in that version.
Excellent! Thank you so much for your prompt and courteous help.
We are back up and running.
(and gussing by your name, please accept my heart’s best wishes for the terrible times in Europe.)