OVPN between 7.6 and 6.48.6

Hello,

I let to connect some clients (6.48.6) to my OVPN server (also running on 6.48.6). Now I added a hAP ac3 with ROS 7.6.
On this device it only works when I deactivate the “Verify Server Certificate”.
If this is also activated on ROS 7.6, I get an TLS error while establishing the OVPN connection.
Why this?

Thanks, a lot.
client_7.6.png
client_6.48.6.png