Hi Manjunath,
To regain the toolbar in Simulink, you can execute the following code in the "Command Window" of the MATLAB App:
>> restoredefaultpath
>> rehash toolboxcache
>> sl_refresh_customizations
If the above step does not work, consider the following workarounds:
- Regenerate the preference directory - Refer to the following MATLAB Answer to know how to regenerate preference directory: https://www.mathworks.com/matlabcentral/answers/99625-how-do-i-regenerate-my-matlab-preferences
- Try a clean reinstallation
- Try disabling firewalls
I hope this helps in recovering the toolbar in Simulink!