I'm guessing you are using the Appigo Sync Toodledo Module? I'm having exactly the same problem: when Appigo Sync runs, I get an incorrect login information error. The admins are right that the problem likely belongs to Appigo. If you watch your network activity (with a program like Little Snitch) you'll see that Appigo Sync makes two calls: one to activation.appigo.com and the other to api.toodledo.com. The problem seems to lie with the first call, because I tried blocking it and Appigo Sync wouldn't proceed further. I've got a support ticket in with Appigo about this, but I don't know when I'll hear back from them. I even tried registering for the free trial of their service to see if they had started requiring a subscription to make it work -- no difference. So it looks like something changed on their side in the last couple of days and there's nothing to be done but wait at this point. I'll post back anything I hear.