1) Here is the indexedDB support:
http://caniuse.com/#feat=indexeddb
Safari isn't supported well.
2) However, the App Cache looks like it has stopped being support without Https. I know Firefox has debated doing this, but not yet. I don't think Chrome has plans for this either. So I'm thinking that might be a Mac/Safari thing.
Let me know more and I can look into it.
One way to ensure it isn't something else is to delete the storage file (where your cookies are) and force the game to load again fresh. However, you lose any existing leagues.
It requires IndexedDB. It is best with Chrome, Firefox, and Opera. The others only give partial support.
Here is the breakdown: http://caniuse.com/#feat=indexeddb
So Apple products don't generally work. Hopefully that changes at some point.
Without IndexedDB the game couldn't be made because it allows the game to run on your computer. Otherwise, we would have to host it and it would become cost prohibitive to have that much processing on our servers.