This issue has been fixed in the latest release of InDesign 15.1.2
Please update to this version to get the fix.
Adobe InDesign team
An error occurred while saving the commentJames commented
Nope, sure hasn't been fixed. I'm on 15.1.2 and I too can't create a reviews "Error getting invited people" (though no one has been invited because I can't even create a piece to review!) Though the situation MIGHT be that the review panel keeps loading my PREVIOUS project for another client. I have shut down and reopened InDesign and not opened the old file. STILL can't get this to work.
As you can see in the screenshot, I have only ONE file open, but the review panel will NOT stopping trying to load an old project. I have closed and reopened ID, reset its preferences, and signed out and back in.