A user is receiving an invalid code error when entering the OTP code from mobile authenticator apps.
It’s likely there is some issue with the mobile device used. A great troubleshooting technique here is to request the user try Authy on the desktop to take the mobile device out of the equation altogether. It’s likely the code received from the desktop will work and it can be proved the mobile device in question is problematic in some way. Most likely the device clock is out by x minutes.