I've played for awhile on the PS5 and decided to turn on cross-save since I picked up the Mac GOG version. Since doing so I periodically get a "The Larian cloud save sync has failed. Please check your network connection" message. Retrying does not work and immediately fails. When I check my Larian account there are no saves listed, so it's simply not working.
As mentioned by tiagofs, Patch 7 is not yet released for console and Mac and will be released in October. That said, if you are playing both on PS5 and Mac, cross-saves should work as they are both in the same Patch at the moment. I would advise reaching out to our support team in this case (if you haven't done it yet!) so they can take a look: https://larian.com/support/faqs/how-to-submit-a-bug-report_85