Open Finder on your Mac.
Go to the Applications folder.
Locate MysteriumVPN in the list of installed apps.
Drag the MysteriumVPN app to the Trash, or right-click and select Move to Trash.
Empty your Trash to complete the removal.
After completing the steps above, restart your Mac, then download the newest version of MysteriumVPN from the official website or the Mac App Store: https://apps.apple.com/us/app/mysterium-vpn-fast-secure/id6446624307