Cannot connect Gateway from Policy Manager on default port 8443.
Release : 10.x
Component : API GATEWAY
The problem was with TLS 1.3 disabled for the listen port which connects to gateway when accessing policy manager.
1. Login to Policy Manager using port number 9443.
2. Navigate to manage listening ports and choose 8443 and click properties.
3. Uncheck TLS 1.0 and TLS 1.1
4. Check TLS 1.2 and TLS 1.3, click OK to save the changes.