Lightroom Classic: Restart sync after using backup catalog not possible

Due a problem with the current catalog, I had to go back to a previous backup.
Installing and general use of the copy is of no problem.

But: Every time I restart the syncing LR tells me "This seems to be a duplicate or automatically created backup of your catalog. [...]". Yes - thats right :-) But also: "To make this to your sync catalog, restart LR and activate the sync" (Hope I translated it more or less correct into English)

The problem is: Every time I do this - meaning to restart LR and start the sync - this message appears.

Do I misunderstand here something? I klick on the "halted" button the in drop down widget in the upper left corner to continue the sync. Or do I have to configure it anywhere else?

Cheers,
Oliver