Geometry problem "unknown geometry -Tag:null"

Hello!

I have done a Chemical Reaction engineering simulation and have synchronized it with a geometry.

The fist model I did was too large, so I wanted to create a new one. I have done this by buildung a new model and also by rearranging the old one.

Now the model won't calculate because it says it encounters the following problem:

"Unknown geometry.
- Tag
Error in multiphysics compilation."

What could be the problem?

Thanks in advance for your help!