Missing Files without an Exclamation Mark

This is a long-standing bug that Adobe has declined to fix: Lightroom: Synchronize Folder shows spurious number of missing files | Photoshop Family Customer Community . Please click Me Too and Follow in the upper-right corner of the bug report. That will make it a little more likely Adobe might prioritize a fix before the next ice age.

Meanwhile, ignore what Synchronize Folder says and use Library > Find All Missing instead.

Willy

Could you recreate this and post a screen shot of the error msg mentioned above?

or post the exact text in that message . . .

Check if you have smart previews for these files. If you do have smart previews, then Lightroom will not show exclamation points.

By the way: you talk about ‘syncing a folder’. If you mean the ‘Synchronize Folder’ menu, then that has nothing to do with online sync and/or the sync.lrdata file.