Hi Pavel Tsvetkov
Firstly, have you made sure your version MultiTerm is also up to date? To do this, if you have automatic updates set, just open MultiTerm and accept any update offered. If you don't have automatic updates, set, go to Help > Check for Updates.
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 an 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.
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 tell them that the problems occurred after installation and, most importantly, 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!