IPSEC VPN - Remote Access VPN stopped working

Dear,

i can't figure out what is wrong.

We setup the Zyxel Remote Access VPN. This was working for a few weeks and now we receive the error "The remote connection was denied because the username and password combination you provided is not recognized, or the selected authenticationprotocol it not premitted on the remote access server".

In the client log i see:

CoId={2B7A7503-3FD7-0003-B371-822BD73FDA01}: The user xxxxx dialed a connection named xxxx which has failed. The error code returned on failure is 691.

In the firewall log i see "generating IKE_AUTH response 2 [ EAP/FAIL ]"

I know the username and password is correct. I created a test user just to be sure and the same error.

I attached screenshots of the whole configuration.

We use the Windows buildin VPN client with the custom certificate.

Please advice