From the query, it seems you are facing this issue on launching Simulink. And I also assume that you are not using MATLAB with the -nojvm flag. That sort of problems could happen because of the path issue or if the cache is not clean. Before you modify anything, please take backup for the existing path definition by using below command on the MATLAB command prompt
>> which -all pathdef
After taking the backup, please run the following commands in the MATLAB Command Window to restore the default MATLAB search path and rehash the toolbox cache:
>> restoredefaultpath
>> rehash toolboxcache
>> sl_refresh_customizations
Following this step, please use MATLAB/ Simulink to see if the problem occurs again. If the problem is resolved, then you may want to save the new MATLAB search path by running the following command:
>> savepath
NOTE: This will remove any custom paths you may have created.
The following MATLAB Answers post is an additional resource on how to back them up:
Here is a resource on how nojvm flag affects MATLAB and Simulink: