We installed SSRS 2019 on a Windows Server 2016 without any problems and configured it to use URLs with port 80.
Accessing those URLs (Service and Portal) via local browser works fine, but trying to access from another server fails. Investigations showed us (checking available ports via netstat) that the Port 80 is only available for IPv6 but not for IPv4. Checked with other ports and always only IPv6 is created and listening.
We also used a portable XAMP installation to check if port 80 in general works on the server and it runs fine, being accessible from outside.
Windows firewall is deactivated on the server. User running SSRS has admin rights.
Any clue why IPv4 Ports are not established correctly by SSRS? (No errors during any configuration)