Symptoms: The PDM Client / explorer login procedure takes 1-2 minutes each attempt.
Examining the network communication and protocol exchanges using Wireshark revealed that among the different attempts to communicate with the server, one is trying to talk to 53470 (65166, 65195 then 65256). To be honest I have never seen any reference to this port in the documentation but I might be wrong.
The solution to my the issue was to open the port 53470 using an inbound rule permitting access on the PDM Server as described hereafter:
Open control Panel -> Systems & Security -> Windows Firewall -> Advanced Settings -> Inbound Rules -> New Rule:
Wizard: Port -> tcp -> 53470 -> Allow the connection -> [Domain, Private] (* Uncheck/Avoid here the public for security reasons) -> Name it then finish.
Check the login/logout/login with explorer -or- Icon tray icon and you should notice the difference.