Hy, I was having the same issue, and as it seems a lot of people too. Im in university so i asked my friends from the year above me if they had the same problem. Basically version 2.2.45 it's the last one where vpcs seem to work. No ideia why tho, just download the .dmg from their github https://github.com/gns3/gns3-gui/releases?page=1

If something else doesn't work just try a ever older version i guess, the life of users of working in process products.