I had a Mac user today on 10.9.5 on a laptop who was trying to open the Citrix receiver, and wasn't getting it to come up. She was able to download the .ica file, and the receiver app was launching, but not proceeding at all. She quit it several times and tried in a different browser, same issue.
After looking at a bunch of things, and then downloading the receiver again, I realized that the receiver had finally given an error on connecting for one of them, saying it couldn't get a response from the server:port. I checked her wifi, and she was on our guest network, which blocks all non HTTP or HTTPS traffic, which was keeping her from being able to get online. Switching the computer back to the regular network fixed the issue.
