IPsec VPN to Fritz!Box not longer working UTM 9.720-5

The VPN connection was working for a long time.
Now Sophos shows that the connection ia active with one tunnel and the Fritz!Box also show a functional connection.
But the tunnel is not working, I am not able to connect to the remote network.
The Fritz!Box was updated to OS 8.0.

IKE: Auth PSK/Enc AES_CBC_256/Hash HMAC_SHA2_512/Lifetime 3600s/PFSMODP_1024/DPD
ESP: Enc AES_CBC_256/Hash HMAC_SHA_256/Lifetime 3600S

What can I do, to find out, what the problem is?
Is there any test software?



The Fritz!Box shows: VPN-Error: IKE-Error 0x203d and 5-6 seconds later: IKE SA: DH14/AES-256/SHA2-512 IPsec SA: ESP-AES-256/SHA2-256/LT-3600 was successful
[edited by: HGA at 4:33 PM (GMT -8) on 4 Dec 2024]