Stopping syncing an old non-existent photo

I am running LRC, LRD on a Mac Studio with Monterey. 

In LRC, I have a photo which is constantly trying to be synced. However, the photo Link is on my previous iMac which is no longer available. 

“Sync has not finished for file 'IMG_5755-Pano.dng. Open Lightroom on Dr's iMac to continue syncing”.

I can find no way to tell LRC to ignore this old, non-existent .dng file, and so there is always one file trying to be synced, and seemingly to consume CPU resources even though there is no other activity on LRC.

How can I force LRC to stop this syncing activity as shown in the Sync preferences?