The next time you open any Google app on your mobile device, Google will tell you it has encountered a problem and ask you to sign back in.

Tap to sign in to your Google account and you will be prompted to enter an email address.
Type in your full Swarthmore email address and click Continue.
You will be brought to the usual Swarthmore login screen. Enter your Swarthmore username and password.
You will be prompted to authenticate with Duo. Choose your preferred method to do so.
1. If you have authenticated with Duo recently, Duo may skip ahead and automatically authorize you.
If login is successful, you will be brought back to your Gmail app on your mobile device.

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