“No available Servers to connect to” when trying to view user PIN status.

Recently, someone asked me if I could check his PIN. Usually, I instruct the user to change his PIN in the Dialin Web Page, but in this case, since Lync Control Panel was already open, I check the PIN Status:

Request failed with error No available Servers to connect to:

The only error was managing the user PIN, so I had to wait for a off-peak to do some troubleshooting.

The first step was to get the user PIN status in Lync PowerShell, running the debug option:

Get-CsClientPinInfo -Identity david.paulino -debug

Basically, Lync Server is saying that no server was found in the pool to connect. This was strange since all servers in the pool are up and running. No Warnings/Errors in Event Viewer.

For those who do troubleshooting, it’s really hard to find the cause when you don’t have any explicit error.

I checked Topology, Certificates, DNS records, and everything looked OK.

Before doing some extreme measures, like rebuilding Web Components, I decided to have a look in IIS Site Bindings.

On internal site:

External Site with the same setting:

Both Internal and External Site were listening in 10.0.0.67, which is the Front End IP Address. This seemed strange, so I checked in another Lync Server 2013 environment and it was listening on all interfaces. The next step was obvious: change the listening setting, so IIS would listen on all interfaces.

After changing in all web sites, I got this result on internal site:

And on the external:

After applying both settings, it was possible once again to check the user PIN status in Lync Control Panel:

I also tested in the Lync PowerShell, just so to make sure:

In conclusion, I believe there is a connection to the loopback interface while managing user PIN. Moreover, if IIS isn’t listening on loopback interface, the error No available Servers to connect to is displayed.