If possible, the best thing for you would be to restore a backup of your site before installing Atum. Is it possible for you?
In any case, take a backup of your site before you proceed with the above suggestion.
**** Important! Please make a full site backup (files and DB) before you proceed with those steps****
In any case, before we proceed, I'll wait for your reply to the other ticket.
Also, please share your site's Debug information with me here. You can read about it here.
Unfortunately, I have a copy before installing the ATUM addon but older.
From the new copies, this option is no longer available.
If necessary, I can share with you a copy of the site BEFORE installing the ATUM multi-inventory addon. Since after its installation there are problems and errors with multilingual CMS