Sorry, this is a problem on the back end: there is a problem with Firefox Account login at the moment for most or all Sync users. Please do not reset your account!

Here's the status page for Mozilla services, indicating they are looking into login problems (as of a few hours ago): https://status.services.mozilla.com/

You might want to try Sync again tomorrow, and just proceed with browsing for the time being. I realize that without bookmarks and add-ons that will not be the same. Do you need suggestions on copying over data manually?

I reset my account. In fact, I made and then had to reset two more.

They might have posted something on the login page. I imagine lots of us spent the last 2 days trying to reset multiple times.

Now what do we do?

You will have to wait until the Mozilla Engineers have fixed this problem on the login server.

See Mozilla — Cloud Services Status:

• https://status.services.mozilla.com/

Firefox Accounts:
We are currently experiencing problems with FxA logins.
Engineers are looking into the problem.