My understanding is that you are getting a warning message when you try to open Simulink. This may have happened because support package would have change some settings in Simulink. Try the steps below to update some of the settings.
1. Execute the following command on MATLAB command prompt. This command refreshes the Simulink menu and dialog customizations. Please restart Simulink and see if the issue persists. >> sl_refresh_customizations
2. If the issue persists after step 1, execute the following command on MATLAB command prompt. This command updates the list of known files (including cache files) and classes for all directories on the search path. Restart Simulink and see if it resolves the issue. >> rehash toolboxcache
3. If the above two steps do not help, execute the following command. >> winopen(prefdir) This will open up a folder in Windows explorer. This folder contains preferences, history, and layout files. Delete this folder by navigating to its parent folder. Close MATLAB and restart it again, check if the issue persists.
If all of the above mentioned steps does not help, try reinstalling the hardware support packages such as Cortex-M DSP that you might have installed recently.
