If you haven't tried already, download/install the revised CB2021 program installer from your online account here: https://www.comicbase.com/mycb/Registrations.aspx
give your computer a restart afterwards and see if you have the same trouble.
*Also, if you have any protection software like Norton, MacAfee, Malwarebtyes, etc. - you may need to setup an application exclusion/exception so ComicBase can have internet access.