Thanks dan1138 for your help.
I can confirm tool pack 1.1.166 for MPLABX v5.40 restores the com port functionality. This is a rough guide what to do.
Plug the dev board into the usb port.
Open MPLABX v5.45
>Packs (3rd option down)
Click Tab "Tool Packs"
Scroll down to PKOB4_TP (list alphabetic)
Locate 1.1.166 Release for 5.40
Click "Install" link
Go to project dashboard
Click Project properties icon
Option categories dropdown: "Tool pack selection" (last option)
Specifically selected version
Programme the device. This will force firmware 1.1.166 to be loaded as part of the process. There may be a way to just load the firmware but I don't see it.
Make sure all your comms settings (baud rate, etc) are the same everywhere.
As a test, if you jumper TX to RX on header, CoolTerm will echo the keyboard.
Jumper whichever pin has the uart output to TX. You should now see your output on CoolTerm or whichever terminal programme you prefer.
Rough guide. Some steps may have been missed, but you should get the idea.
Hope it helps.
post edited by ashdash - 2021/01/25 12:42:38