When new Authy multi-device installations are configured on an existing account, any previously configured 2FA account tokens should be synced to the new device. If you're missing any 2FA account tokens on one or more devices, check the Authy ID on each installation to verify that it matches on each device. Multiple Authy IDs would indicate multiple Authy accounts are configured on your devices.
If you do see multiple Authy IDs, find device that shows your current phone number (on the same screen as the Authy ID). You'll want to make this your main Authy account going forward. To help make sense, we'll refer to this as your "main Authy account" for the rest of these troubleshooting steps.
To sync any missing 2FA accounts to your main Authy account, follow these steps:
- For each 2FA account missing on your main Authy account, login to the account’s corresponding website using the code on your other device, and then temporarily disable two factor authentication.
- On your main Authy install, remove all devices except for the one labeled as “This Device”.
- On your main Authy account, Re-add your 2FA accounts.
- Make sure that Multi-device is enabled, and then uninstall and re-install Authy on your original device.