I couldn't find an answer to this question.
Mac mini, iOS & Mac air.
Mac mini, 17874 photos - says 1 photo to sync (remains stuck)
Mac air, 17874 photos, says sync complete
iOS, 17873 photos, says sync complete
Lightroom Web, says 17875 photos.
problems now fixed - 57 photos sync stuck Mac mini, cleared all but 1 with selecting flag trick (sync stuck saying 1 photo (current problem))
Mac mini had 3 photos that said were synced, but in fact were not on the other devices, photos found and deleted from library of Mac mini - reconciled photo totals for Mac mini and Mac air.
Have tried restarting, clearing cache (iOS) and signing in and out of all devices.
Current problem - Mac mini still says sync 1 photo, and numbers miss matched on other devices.
Mac mini - When selecting cloud icon with option key to see what is syncing, shows a blank screen.
I have no idea what else to do sorry.
1 photo sync on Mac mini frustrating, would just like all to reflect same, humbly seeking help
Thanks in advance
To correct iOS device, uninstalled Lightroom CC app and reinstalled, this then corrected total number of photos between iOS and MacBook Air.
Next managed to correct Web number by finding and deleting a file that had not synced correctly (labor intensive job of checking each year, then months total photos until mismatch found, then used 'flags' to id file that hadn't synced (on MacBook Air select all photos in that month, select 'flag', wait for sync, then go to same month in web and filter all photos not flagged - showed unsynced photo).
So now after following these steps above have MacBook Air, iOS and Web interface correctly showing. Do not have Mac mini in front of me yet but hoping error will correct itself - will advise
Update: Mac mini now correct synced ups reopening.
I don't mind using Lightroom CC, but it would be nice if they provided some useful diagnostic tools to assist in finding problems.
My only other experience with cloud photography is apple photo's, same photos imported their, no issues like this encountered.