Error: You can’t view this item in Lightning Experience. Open in Salesforce Classic

This is a weird bug in Salesforce that sometimes happens when a license is added and then it (Salesforce) reveals objects. You can try refreshing the user’s cache by viewing the Profile (Top Right) and changing the display density to Comfy or Compact, whichever its not set to. Then change it back. Otherwise the member of my team who has seen this error, he says he has seen it correct itself after a day.