iCloud photos not syncing to Mac

I have iCloud Photos activated on all my devices. 5 days ago iCloud photos stopped syncing with my MacBook Pro. iPad and iPhone syncing fine. Have restarted all devices, force quit Photos on Mac. But still will not sync. Some advise deactivating iCloud photos on the Mac and restarting. When I start that process I am prompted to "download" or "remove from Mac" before proceeding. If I select download, the number of photos it says it will download is not the same as what appears in my photo library. Am I risking loosing photos if I turn off iCloud photos on this one device? Do I really need to download over 5K photos? Any other advice about getting Mac to sync to iCloud photos?