Just for Ref in case anyone else experiences the same issue. I managed to figure it out. I ran the game on my Seris S no problem the Altitude setting is clearly visible. I then checked all my in game settings and made sure my Seris X mirrored those of my S. Everything was the same. Something else strange when I take a screen shot, in the picture I take you can clearly see the Alt setting.
I then checked my Seris S visual settings against my X. I found it. During the setup of my X I enabled Dolby Vision Game as I understood the Sim supports this. This is the culprit, so unticking this setting solves the problem. Not sure why this happens but at least it’s sorted.