Game Launcher Closes Somewhere between Log-in and Patching

I've played TERA using Steam since Gunner release with no major issues that I've not been able to fix. Logged in last night after a two and half week break, bought EMP through Steam, used that to buy a 30 day Elite Status Voucher, popped the Voucher, restarted my client and happily did some warm up dungeons like I usually would after a break.

Today, started up, loaded TERA through Steam and the Launcher closed after log-in, but before it had done the patching and never re-opened. Re-tried through the Steam Launcher and then the TERA-Launcher.exe executable several times with the same result.

The only thing that appears to be different between today and yesterday is that yesterday I started my gaming session without Elite (even though I applied it within 10 minutes), where today I had Elite at the start of my gaming session (having applied it yesterday).

I then worked through all the documentation listed below, firstly through the Steam Launcher, then through directly executing TERA-Launcher.exe, then Steam Repair before trying Steam Launcher and TERA-Launcher.exe again, then uninstalling and installing TERA through Steam to get a fresh install and then repeating the steps with the Steam and then TERA-Launcher executables:

TERA Launcher Will Not Start / Is Already Running:

• Running TERA as admin can only be done through executing TERA-launcher.exe directly, and that was just taking me back to the log in screen. I can log-in fine here and into Support so I don't see why I can't log-in to the game.
• Adding TERA as a trusted program didn't work in all 4 different attempts
• Update WIndows. I run Windows 10. It updates itself and all the drivers it can by itself
• Manually Update Your Root Certificates (Advanced troubleshooting). Did Nothing.
• Delete Your "game.version" File. Did Nothing.

Failed to initialise launcher
This didn't do anything because I would have the same symptoms. As non-admin, the Launcher would close after log-in. As admin, I would log-in and then get taken back to the log-in screen. This meant that I couldn't not accomplish the last step.

TERA's Launcher Settings
Seeing as this requires the Launcher to have made it past the log-in and patching process, this is not possible for me to complete because the Launcher doesn't even get past the patching process.

The Launcher is Not Loading
Tried unchecking all the suggested boxes and this had no effect.

Repair TERA To Resolve Common Issues
Repair through the TERA Launcher is not possible because the Launcher won't progress past the patching stage before closing. Steam Repair was already mentioned above.

Anyone got any ideas on where I could go from here? I'm currently waiting on two support tickets to be resolved, so I can't submit this as a support ticket yet (why is the limit for support tickets two at a time?).

Other games work. TERA for EU works. Everything but TERA NA works and I'm stuck on what to do to try and fix it.

PS: Also, rip that Elite 30 Days I popped yesteday. It looks like I won't be able to make use of it until I resolve this.