Problem syncing between Lightroom Classic and Creative Cloud and vice versa

Hi. Please see the screenshot above of the number of total photos and synced photos on my iMac, where I'm running LrC. Ignore the Missing Photos bit as I know how to resolve that issue.
I use Creative Cloud, Lightroom Mobile and Lughroom (the latter on my MacBook).
I upload new photos always now to Lightroom on the MacBook, although that hasn't always been the case. Everything apart from LrC has the same number of photos on it (25,742). However, it is clear that there are some photos that have not been downloaded to LrC from Lighroom/Cloud/Mobile, and also some that are on LrC that have not been uploaded to Creative Cloud and therefore my other devices.
I uploaded a bunch of new photos to Lightroom on the MacBook yesterday. They also appear on the web and Mobile, but haven't downloaded to LrC on the iMac. Equally, there are a bunch of photos on the iMac which haven't uploaded to the web and the other devices.
Can anyone please advise on how I resolve this please?
Thanks. Simon