This error means that you're not on a team or in a security group with the person you're attempting to connect to. You'll need an administrator to put you in the same group or on the same team.
If neither you nor the host use Parsec for Teams, then the error means the link being used for the connection is invalid. Try using a new link and confirming that it is correct, or try a different method of connecting to the host (via the Connect button in the Computers tab for example, if you are both friends).