SWV ITM stopped working (2 boards)

Hello,

It worked for about a year or two but was found to not work when trying it after some weeks. I have checked the obvious items:

Enabled in Project properties Debug

I am using the standard code

although, on a breakpoint there, that value should not be zero, but doing

ITM->TER |= 1;

makes it 1 but does not help.

Then this button needs to be clicked

What could cause this?

AIUI ticking that box at the top screenshot enables the debug macrocell.

And SWO wire is connected. These connections have never been changed. I have swapped over the debuggers (2 x STLINK V3, ISOL and non ISOL, STLINK V2 which I think doesn't have ITM anyway). Tried different SWV speeds e.g. 1000kHz.

Something else is broken.

I would be grateful for any ideas.