Hi,
Try using FQDN. When logging using SAP GUI, it would show you the entire domain name of the application server, say for example: scn.sap.com . But when you open some services, it could get cut to http(s)://scn:port/servicePathHere notice that .sap.com got omitted and the webpage will usually result in an error or blank. If that does not work, use IP address instead.
Another reason could be your PI system is using load balancing, try running it in the central instance.
Regards,
Mark