A few thing that have sometimes helped me when I get crashes in franchise mode:
1. Try (re)-validating your steam files.
2. Try going into another franchise zoo and cleaning out your trade center completely (move animals to quarantine or into habitats elsewhere). Sometimes having an empty trade center has made it so that my crashed zoo will open. I'm not sure why, but it sometimes helps.
3. Try a few times. Sometimes it will crash on me once or twice, and then magically open up for no reason.
4. Try again the next day. Since the problem may be connected to the steam server or franchise server, and can sometimes fix itself whenever these roll over.
5. If none of these work, you may need to wait until the next minor update (1.9.1) as sometimes this has fixed it for me. I also try again whenever there's a steam update, windows update, etc... just to see if anything fixed itself internally.
6. And unfortunately, for one of my zoos I've never been able to reopen it after it began crashing, so let's hope that's not the case for you.
Good luck!
