NotHisRealName, you might try logging in at the standard site on your phone and then switching over to m.fuelly.com once you're logged in. If you're logged in at the standard site you should also be logged in at the mobile site.

That's a very unusual error, so simply using the different form could be a fast way to get things working.

I tried, but had no luck. Logging into the standard site first seemed to make no difference.

Were you able to log into the standard site and a fuel-up from your phone there? I'm wondering if you have cookies or JavaScript disabled.

You might also try clearing your browser cache.