Flight Data not appearing on monitor

I have quadcopter with a Pixhawk PX4 2.4.6 and 3.4.6 firmware, and MinimOSD. The OSD display the titles of the data I wish to have, but no data is returned from Telem2 port - except the mode selected. Mode is the only item that displays, it changes as I switch modes. I have compared parameters with another PX4 on my Hexacopter; they are the same.
I had this MinimOSD connected to a MiniAPM 3.1, it correctly output all flight data. So I’m confident that the OSD is Ok.
I tried 'Enable Telemetry in Initial setup, this did nothing.
Any ideas please?