Ok I would next then try uninstalling eM Client and “don’t delete the database” when asked on the uninstall wizard. Then go to the release history page and download the same version and reinstall and see if the popup confirmation appears when you drag or right click to change the category. See my example screenshots “further up this thread” of what normally happens when you eg: drag an email subject to another Inbox Category.
If uninstalling and reinstalling eM Client still doesn’t bring up the change category confirmation prompt, then “try manually repairing the database” as per @Gary post in the following thread link.
Note: Before running the repair make a manual backup first via “Menu / Backup” incase you need to restore for any reason. You can see when the backup is complete in Show Operations via clicking the drop-down on the right of Refresh top left.
Now if manually repairing the database still doesn’t make any difference , then I would next suggest to “try a new database” incase yours is corrupted in some way. So if you have an IMAP, Exchange, Office 365 or iCloud account and nothing in eM Client Local Folders, then “close eM Client” and go to the following hidden database folder and “rename it to eg: eM Client-Old” and then reopen eM Client and setup as new and see if that brings up change Inbox category confirmation prompt.
(Windows hidden eM Client database folder)
“Users\yourusername\AppData\Roaming\eM Client”
(Mac Hidden hidden eM Client database folder)
“Users\yourusername\Library\Application Support\eM Client”
Now if a new database still doesn’t bring up the change Inbox category confirmation prompt, then close eM Client and “delete the new eM Client hidden database folder” and then “rename your original eM Client-Old database back to eM Client”. Then reopen eM Client.
Alternatively if you have been been making regular eM Client backups either automatically via the Settings or manually via the Menu, then you could optionally try restoring a recent dated backup “when you know the change category confirmation prompt was appearing”.via “Menu / File / Restore” Any new emails etc since the backup will then appear when eM Client reconnects.
Lastly if you still carn’t get the change Inbox category confirmation prompt to appear, then if you have a current active paid Pro or Personal version suggest next to go to the VIP support page and login and lodge a support ticket.