This can happen if you accidentally lose your phone or need to wipe it. There are two routes to getting access back:
Use a Backup Recovery Code
If you've been a very good and read the instructions when setting up 2FA with OneAuth then you'll have some backup codes you can use to log in.
Use one of the codes (then strike it off so you don't use it again) to log into the webmail (
www.parish-online.co.uk/email-login) then you can go to the 2FA settings again and set up your new phone with OneAuth. You'll have to store a new set of backup codes.
Ask your clerk to Reset TFA
If you didn't save any backup codes, after you've spent 10 minutes on the naughty step, contact your clerk who will be able to log into the Email Admin Panel, go to your user profile and click Reset TFA. This will allow you to log in with your gov.uk email address and password, then set up TFA again.
Clerk needing a reset
If you're the clerk, you'll need to contact Parish Online support. Use your personal email address but copy in the gov.uk address you're trying to access.