SecurEnvoy 2FA and FortiClient

We have and Fortigate 100D and configurred to authentacate using SecurEnvoy server and currently only use the SecurEnvoy IOS APP to provide the 6 digit auth code and/or PUSH

This was working successfully and all of a sudden has stopped; the FortiClient logs staright in but the SecurEnvoy authentocator APP still recieves the notification.

Amy ideas why the 2FA field doesn't appear, normally at 45%?

Thanks

Sharpy