I’ve managed to some how change the settings of my sketch so when using the orbit tool it won’t allow me to go inside the building walls. Its also changed the settings of the positing camera tool (the one with the man standing on a red X). when I used this and place it on the floor inside the walls it takes me to that point but shows the model as an elevation in line with the placement.
Any chance you are in parallel mode ?
Check in camera menu, perspective makes the camera move like a physical object, it can clip inside walls and move around.
Parallel (my preference, but I’m greatly outnumbered here) don’t allow you to enter a wall and will kinda show you elevations when using the positioning camera tool.
That was my original thought but unfortunately wasn’t the cause. I’ve tried purging the model and I reset the field of view back to the default and non of that seemed to work either 
Can you share the model?
Does ‘Height Offset’ (default 5’ 6") have anything to do with what you experience?
p.s. Your profile says you are using SketchUp Pro 2023 , yet your ‘Position Camera’ is a man standing on a red cross.
https://help.sketchup.com/en/sketchup/walking-through-model