Hello Nicolas,
I understand that you are trying to install a Simscape multi body add on but getting an error.
The warning message saying that the file is already open is because there might be an instance of MATLAB running in the background. The error saying “An internal error has occurred” is because there might be some permission related or file access related issues. To remove the warning, first close all the instances of MATLAB that are open or running in the background. To remove the error run MATLAB as an administrator. This will resolve the error.
You can refer to the below documentation to learn more about Simscape Multibody plug in:
You can also look at a similar question that was answered by MATLAB staff:
Hope this helps.
Thanks,
Charan.
