Uplay troubleshooting
Reinstall Ubisoft Connect client to fix the issue.
Ubisoft Connect client has to be started at least once (and user must be logged in) for Playnite to import all games properly. Ubisoft Connect doesn't have to be running for import to work, only initial authentication in Ubisoft Connect is important.
If you are still having issues then try deleting c:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\cache\configuration\configurations file, restarting Uplay and then try import in Playnite again.
Ubisoft Connect has to be started at least once after new game is added to your account for Playnite to properly recognize it.
Games that were bought from a different store (like Steam), but require Ubisoft Connect to launch, won't be imported. It's done that way because launching those from Ubisfot Connect still requires that original launcher (Steam for example) to be installed and it would create unnecessary duplicates. Only Ubisoft games bought on Ubisoft store or those that don't require 3rd party launcher to start, will be imported.