I am trying to generate a FEM mesh, and according to the tutorial, SimNIBS is the best option to do so. I followed the installation instructions for SimNIBS to be installed, and found the SimNIBS GUI (which should indicate that SimNIBS has been installed correctly). However, when trying to create the FEM mesh, I get the error that SimNIBS is not installed (see picture below).
The problem was maybe not the installation folder, but the configuration of the system path.
When installing SimNIBS, there is maybe an option somewhere to allow this install program to edit the system path and add the SimNIBS/bin folder to it.
After the system path is modified, Matlab must be restarted.
Installing SimNIBS and not restarting Matlab after would lead to the error you reported.
To edit the system path manually on windows 10:
Click on the Windows button
Search "environment" and click on "Edit the system environment variables"