Here is the Arc Menu in action:
Normally I can update it via either Google Chrome or Firefox using the Gnome Extensions website however tonight when I tried the update an error occurred.
The menu was also missing and I tried to reinstall, reboot and all the usual turn it off and back on again tricks but to no avail.
After some duckduckgo’ing (I am trying duckduckgo as my default search these days over the evil Google), I came across the solution of restarting Gnome.
So for anyone else that needs this solution or for me if/when this happens again here is what to do when you see the error.
Press Alt+F2 to bring up a dialog then type r to restart the Gnome process.
After a refresh, the menu should be working and the error will be gone.