I've had this problem a couple of times now, and I can't find a fix:
1. I add images to a collection in Classic, then right-click->Sync with Lightroom CC, the Make Public and send the link to a client.
2. In Classic, if I click Help->View your synced collections on the web..., then click on the Collection in the browser window, all images are there and it says "Shared" under the Collection.
3. However, if I open the public link, a number of images are missing (in one case six from 26, in the most recent case 24 out of 53 are missing.
4. In the second case, dumping the images into a new collection in Classic and repeating the steps above fixed the issue (the new link had all the images), but for the first case this didn't work.
I am running the current version of Lightroom on a late 2016 MacBook Pro which is also up to date. In both cases the galleries had hours to sync, and I'm checking four days later in the most recent case.
I've done this hundreds of times and it's been fine. I am nowhere near my 20GB quota (currently using 4MB - I'm guessing this is because mine are almost exclusively Smart Previews).
Any ideas what's going on?
Wondering if you have moved to a more recent version of LR Classic recently Kev or installed a system update perhaps between problems?
No on the LR Classic update - I actually updated today (before I got the message that the second gallery was missing images).
I checked the InstallHistory plist and don't see anything other than Pages / Numbers on the 6th (after the second gallery was created). and a few other unrelated apps updating in October (the shoot for the second case above was on Friday Oct 5th, gallery created October 6th).