I cannot connect to another machine because it says they are running an older version BUT..
Another person RUNNING THE SAME VERSION AS ME CAN CONNECT.
Why can they connect to that machine but i cannot????
The free license users have many features to use, but they can't connect to previous versions of Teamviewer, as this is one of the extra features the licensed customers have.
If you want, of course, you can take a look at the licensing website and unlock many extra features after buying a license.