SSL Remote Access does'nt work with Port 443

Hi,

at home i use an XG Firewall with Firmware SFOS 16.01.2.

My customers has all UTM 9.x with configured SSL VPN. Every UTM is configured with an random Port e.g. 4422, 4323, 4343 ....

One customer has an UTM with Port 443 configured for the SSL Connection.

With my XG Firewall i can connect to all customers with Port 4422, 4323, 4343 .... Only to the costumer with Port 443 i can't connect. If i change the Port on customer UTM to 4422, 4323, 4343 .... the connection works flawless.


I doesn't have any https scanning active nevertheless i created an exeption for that.

Sadly it doesn't work. I can't see any blocked connection in log.
Https in webbrowser works without problems

Can anybody help me?
Thanks!