LrC doe ot sync pics in a particular folder

I exported the photos and deleted them from LrC then imported them back into a new folder.  The created collection synced properly. I have no idea why i had this issue. Other photos imported from the sane roll the same way synced properly. I can only guess that there was something wrong with the sub folder. 

Smart Collections are the one type that cannot be synced.

What is different about the photos in the collection that will not sync? Are they different in any way to your usual images?   A different camera? A different file-type? Downloaded from somewhere? etc.

Do the previews in grid view  show an exclamation mark on the border that might indicate the files are missing or corrupt?

Can you show the files in File Explorer by a [right-click] on the preview?

I’m not sure that exporting and re-importing will be to any advantage, or simply [remove] from the catalog and re-import.

Can you post a screen-clip to show the grid of previews with the problematic collection selected and shown? 

We appreciate your posts in this forum so that others might also gain from the thread posts.

Any chance it happens to be a Smart Collection?