Mmm, I was hopeful that old saves would be compatible, but it looks like they are not. If you would prefer to play older versions of the game to continue your old save file, they are available on the tfgames.site download section. Otherwise I apologize for the bother of the old save not working.
I'm fine with starting a new save, especially since my character was really struggling in that playthrough. That being said, a lot of people in America can no longer access tfgames. The site has blocked access to anyone that lives in a state that requires age verification to visit adult sites, instead of just ignoring that requirement like all the smart sites do.