This feels like something went wrong with the support package installation. What is the output if you type which -all arduino in your MATLAB Command Window?
If it says, 'arduino' not found I would think you have to perform a reinstallation of the support. For this:
1) Type this command in MATLAB and note down the location - matlabshared.supportpkg.getSupportPackageRoot
2) Uninstall the support package
3) Go to the location from Step 1 outside of MATLAB and ensure all files related to your support package are gone, if not manually delete them
4) Close MATLAB and reopen as administrator
5) Install the support package