Hello hesander,
I am not able to reproduce your problem with a fresh install of the toolbox.
Can you try and reset the MATLAB path? For that you should go to MATLAB Home tab -> Set Path -> Click on Default -> Then click on Save.


and then run the mbd_mpc_path script so you install the path for the toolbox over a fresh, default MATLAB path.
Note: you will lose other paths other than the default + MPC toolbox paths by doing this. Consider saving the current contents of your MATLAB path (you can get it by typing matlabpath in the MATLAB terminal for instance).
Note: this file is located in {INSTALL_ROOT}/src.
Kind regards,
Razvan.