midi plays then won't record

Trying to get a midi track to record.
I can play a synth (Dexed) on a midi channel and it appears in the vu meters for that channel and I can hear it.
As soon as I hit record and try the same thing again the vu meters no longer operate and nothing gets recorded although I can still hear it.
Any tips or tutorials appreciated.

Do you have other tracks in the project? If so, you probably have to select the IN button in the editor mixer on the left, then arm the track and select rec-play

Mmmm, thought I had tried that
Here’s a screen shot
Your help is very much appreciated.