Cannot start a meeting with the app

Hello everyone. 

I cannot start a meeting with the app, I tried to run the program as administrator but the host button does not start anything. After several attempts the system offers me to host the meeting through the browser but you lose a lot of options like drawing on the meeting window. 

I uninstalled (also a big issue) and reinstalled to no avail. I work on windows 10. Any suggestion?

Thanks.