Unexpected content from server (got JSON) keeps popping up)

So I found that in order to get rid of this error you must delete the app and its cache entirely 

I have an iPhone 12 so I went to setting —> general —> iPhone storage then find app and delete it from there. 

once done redownload the app add your birthday you originally associated with your old profile and it should find any profiles you have saved. 

that should fix the error you keep getting I’ve done it twice on two different devices and it worked for both.