Q: Duo - resync D100 hardware token

I have a Duo D100 hardware token that used to work, but now it seems to have de-synced - the codes that it generates do not work.
How do I get it re-synced?

Answer

The Duo D100 codes are event-based, and if the button is pressed too many times, the codes can go too far ahead of what the server is expecting and be rejected.

You can resynchronize the D100 by going to your "manage devices" page on duo.mit.edu and using the "Resync token" button.

1. Go to https://duo.mit.edu/managedevices/
2. Click "Resync token" for your D100 device
3. Provide three successive codes from three button presses.

Other options

If the resync does not work, try removing the D100 hardware token and then re-adding the D100 hardware token to your account.