You can fix the rejection for prior year AGI/PIN mismatch on a mobile device by following the steps below:

1. Sign in
2. Click the My Taxes tile
3. Open the return
4. Click the three-line menu in the upper left
5. Click Filing
6. Click E-file
7. Continue through the steps until you reach a page titled "We recommend using your 2018 AGI to verify your identity."
8. Make the appropriate selection and continue through the steps