Try this, Right click in steam, properties, Local files, browse local files, righ click launchpad.exi, click properties, click the compatibility tab at the top, the click change setting for all users and check run as administrator, after this close everything and try to re-open the game by clicking play in steam. The game started up for me after this.
Things to note, I am using windows 8, I am also not a BT user.
I was having the issue when clicking play nothing would happen at all except for the H1Z1 icon appears for like 1 second and nothing would happen. This fixed that issue for me.
If you have windows firewall turned on after you get logged in a window will pop up in the background so you will have to tab out click "allow access".
This fix got me into the game. I hope this helps