I’ve tried Googling for the answer to this question, to no avail. Now before you call me out:
I DO OWN GARRY’S MOD.
I AM NOT TRYING TO CREATE A SERVER, I’m trying to join a couple of friends in the server they are in.
I’m simply able to get all the way to “Sending client info”, and once I’m about to enter, I get the “Steam Validation Rejected” pop-up.