[2021] Failed to synchronize achievements with the cloud

Hi Farvay! I'm sorry to hear you're running into this issue playing Anno 1800. As @AORUS2017 mentioned, I do recommend verifying your files as a first step.

If the issue continues, you can give the following steps a try:

1. Open Ubisoft Connect as an administrator, then go to settings.
2. Untick "Enable cloud save synchronization for supported games"
3. Make a backup of your save games
4. Remove the save file from the original folder
5. Launch game and play until the game autosaves or you manually save
6. Quit the game, enable cloud saves, and launch the game once more
7. Select local save when prompted

Thanks for coming back to us about this, @farvay - I'm sorry for the frustrating time you've had with Anno 1800 and Ubisoft+.

There isn't any way to disable achievements entirely with Ubisoft+, since offline mode cannot be used with that service. Instead, though, I'd like to invite you to run through our connectivity guide, as this will make sure your connection to our servers is working as it should. In particular, from that article, please remember to reset your network hardware, switch to a wired connection (if possible, and if you aren't already), and check for software conflicts that might be causing interference.

Please also take a peek at our ordinary troubleshooting guide. Since you'd disabled the cloud sync, I'm unsure if you'd tried the steps Ubi-Mushy had suggested, but one of them included running the game and Ubisoft Connect with admin rights, and you'll find steps to do that linked in the guide.

If you're still experiencing issues after those steps, please let me know, as we'll be able to help further with some system files from there.