I’m commenting to hopefully revive this thread for some attention as I’m having the same issue and have tried the same troubleshooting steps. Mine doesn’t work with any theme, either.
While I don’t believe commenting out a vulnerability fix is the answer, improbablejulia, could you find out specifics of what the fix is (name, article talking about it, etc) so others of us not using Pair can ask our domain hosts about it?