Hi @paddyclown,
Best post issues with IFC manager here: https://forums.sketchup.com/t/sketchup-ifc-manager-extension/
You seem to run into this issue: Apparent problem with Sketchup 2023 · Issue #44 · BIM-Tools/SketchUp-IFC-Manager · GitHub
And yes the Sketchup team did give a heads-up, I encountered some issues with REXML it the alpha versions but I’m unable to reproduce is with the released version, not even on a completely fresh PC.
It seems to fail on loading the skc schema as a REXML document.
I will look into it…
Cheers… Jan