Messaging Link has vanished

Hi I have almost the same problem as reported in this closed topic from three weeks ago.
Messaging missing from the dropdown and in Safe Mode.

I have messaging switched on. Unlike in the linked topic.
I am Trust Level 4 - Admin. and this is the level I have set to use the messaging system.
All Users are Trust Level <= 3
I want the messaging system off.
Leaving it on was an attempted work around the Message link for Staff not showing as previously reported by @GI-Joe .
It didn’t work either but may give a clue where to look for the problem.