I just downloaded and tried to install the Episode 4 patch (from the final season.) and it's saying it's not the right version. I have the episode 3 patch applied.
I had the same thing happen. I fixed it by doing the following. I use the offline backup game installers and used this file (22 MB) to patch my episode 3 game:
Patch (220.127.116.11 (52:13) to 18.104.22.168 (53:13)) 22.214.171.124 (53:13) 22 MB
then I used the 1 MB file to patch it after the 22 MB file:
Patch (126.96.36.199 (53:13) to Episode 4 (188.8.131.52)) Episode 4 (184.108.40.206) 1 MB
and it upgraded to episode 4 for me.