@michaelderekjones Who would have thought, getting a fresh copy from https://postman.com/download and installing that fixed the issue, despite it being the same version that I had earlier (I did not even remove or clear my existing install!!)
You may also want to try clearing the local install of Postman before doing a fresh install and test again. (Make sure you remove all folders as mentioned in that article)
If nothing works, I suggest you reach out to Postman support