That being said, I checked my server logs and I see many connections from my home network but only one from my work network, even though I have left and returned to my work network several times.

It may be that something is stored on the N9 during the first connection attempt. If you are still experiencing problems, I suggest deleting the network connection and creating it again.

It seems connectivity-test.ext.nokia.com came back online on 2016-01-04.

Edit: My reasoning is my home network connection was probably created before my server was up and running, and my work connection was created after.