strange behavior on ipsec vpn

Following constellation:

FortiGate with FOS 7.2.10

FortiClient 7.2.5 on windows.

IPsec tunnel witb psk and xauth against ldap usergroup on Authenticator and mode config.

Behavior:

- Tunnel connects

- does psk auth and proposals

- does mode config - gets ip and everything

- initates xauth

- fgt send xauth request to client

Log on FGT reports "Client has not completet xauth challenge" even before the forticlient prompts me for 2nd factor.

Looks like FGT sends the xauth request but does not wait for an answer from client.

Do you have any suggestions?