Decrypt website traffic SSL/TSL

Having an issue with decrypting traffic from a game, not trying to cheat, just trying to scrape the leaderboards off :)

In Environmental Variables, I've set SSLKEYLOGFILE to a text file. The file filled with all sorts of stuff, CLIENT_RANDOM and RSA things.

I've then gone through WS and set PRE MASTER SECRET LOG FILE to the above file.

I have then started capturing with the filter TCP == 443 and loaded the website. Loads of packets come in, the sources are 2/3 different IPs. However, the packets do not seem to decrypt and I'm still left with the garbage text.

I've set the log file for SSL also but that's empty apart from these few lines:

Wireshark SSL debug log
Wireshark version: 2.0.4 (v2.0.4-0-gdd7746e from master-2.0)
GnuTLS version:    3.2.15
Libgcrypt version: 1.6.2

Any ideas how I can read this SSL/TSL feed in plain text or what am I doing wrong?

Thanks in advance.