If the problem is still lingering as of today, make sure you're running with our latest build for CB2020. The current build is 20.0.1.2878 which you can download here: https://www.comicbase.com/mycb/Registrations.aspx
Also try restarting Sidekick (or restart your computer) then attempt to 'Save to Cloud' with Sidekick.
If you still have no luck, please email us at support@comicbase.com, provide your UserID and we'll look further into it.