I just downloaded and installed two new games to my GOG game library, and the games installed beautifully! But, when the installation process ended, I am getting a message saying that there is trouble syncing my cloud saves. I don't entirely know what this means, but I am hoping someone can tell me how to fix it. Thanks so much!

Uninstall galaxy...

Galaxy has a function where save files from your machine are copied to the web, that is what has broken. There is a size limit to your saves on there. From what I have read you can delete saves from in games, probably Witcher 3 saves. Me I wouldnt use such things. Download offline installers and no need for galaxy at all. Copy save files anywhere you want, anyhow you want and don’t rely on internet, win everywhere!

Probably a problem with the GOG servers, or your connection, or both. You can try pressing retry/resync; if you have luck the process will refresh itself. If not, the saves will sync later, the games use to sync themselves when launched and at game exit.

Greetings

I had (still have?) a similar problem recently. When I quitted Divinity: Original Sin 2, Galaxy wouldn't sync my saves and the play button was greyed out until I restarted Galaxy. The solution: I went to the game's folder and created a shortcut to the exe. That's the good thing about GOG. You don't need the client to play your games.