@comtech - I may have the solution for you, assuming you have not received anything yet. I did some more digging and came across this post:
https://community.freepbx.org/t/zulu-is-disabled-and-i-cant-upgrade-it/49902
After I went under “Settings > Asterisk Sip Settings”, I went to the “PJSIP Settings” tab. Under “Transports”, I set “ws” and “wss” both to “YEs”, then issued a ‘fwconsole restart’ from the command line.
Once I did that, I was able to upgrade Zulu no problem.
Unfortunately (for me), the system I did this on was the system not exhibiting the “Whoops!” page error when I go into “Inbound Routes”, as they are a much busier system then the one I just did it on (I waited until there were zero calls going on before I restarted Asterisk). For the system with the “Whoops!” page, I will need to wait until after hours (for them) 
I will update here once I have tried the other system too.