uploading mpfb-avatar to opensim

[ToshaT]

What on earth do I do wrong?
I am new to MPFB after using MakeHuman way back when and only ocasionally.
Now I follow the tutorials about making an avatar in Blender (v.3.4.1) with MPFB (v.2.0-a1) step by step and very exactly...
Before exporting the selected body and armature I use the options:
- Only selected
- Include armature
- Include shape keys (or not, makes no difference)
- Deform bones (or not, makes no difference)
- Export to SL/OpenSim
Everything works well until I try to upload the avatar to opensim via Firestorm (v.64 6.6)!
This is the result:
Avatar wears OpenSim-System clothes and hair and the "Weight" button is greyed out.
I would be delighted, if anyone could lend me a helping hand!

[joepal]

I sent a reply as a PM.

My hypothesis here is that opensim doesn't like the helpers, and that removing these might improve the situation.