Firstly, have you made sure your version of Studio and MultiTerm are both up to date? If you don't have automatic updates, set, go to Help > Check for Updates. It's important to have the most recent version of Studio and MultiTerm.
Then, have you tried a Windows Repair of Studio via Control Panel? Instructions of how to do this, plus other ways to reset your Studio/MultiTerm setup, are given here:
Performing the first suggestion, a Windows Repair, is helpful with any heavy-duty software, especially after a Windows update. It should always be possible to run a Windows Repair. You may need an extra/different click somewhere (at the 'Small icons' step for example) to get you via Control Panel to the right screen. It depends on how your User Interface is set up. You can also find Control Panel by typing it into the 'Type here to search' box next to the Windows button bottom left of your screen. Then follow the instructions on the above link.
Regarding the 'reset' suggestion on the above page... Before you delete or rename settings files, you may wish to first save your user profile settings via File > Setup > Manage User profiles > Export... (there is always the slight chance that they are causing the problem but then you can do it all again without importing your profile settings). When you've finished the 'reset' process, you can use the same path to import your profile settings.
If these suggestions don't help, try reinstalling.
If that does not work, you can then get free help with licensing and installation issues that are preventing you from working, pretty fast:
Fill in the form here:
Select 'installation' from the 'Case type' dropdown and give your correct email address so that they can contact you.
I hope that you can find a solution in amongst all of the above!
All the best,