At my company, lots of issue with this. But this ongoing this is really (other than format, layouts that's unlikely unreadable), is just due to parsing the wrong information, and upon saving, the site does not explain why it doesn't work, just simply ignoring the button click.
Solution: make sure major fields like first name, last name, email, etc. and in my recent case, Candidate Name was linked to wrong info, so I unchecked Candidate Name, and it should work.
I was led to the solution hint site above after doing a Developer Tool inspection on the site and then googled: errors.cannotPersistEntity