How to solve 'Valid Chart Product Not Found' after USB disconnect from Garmin Watch?

The error Valid Chart Product Not Found shows up in BaseCamp for some maps that are on my Enduro2. Reason was an inadvertent disconnect of the USB connection to the watch while the maps were in the process of syncing.

How can the sync process between watch and BaseCamp be re-activated, to make the corrupted maps available again in BaseCamp ?

I believe it has to do with clearing the local cache - but how / where?