Alternatively...

I discover that I can get onto our web catalogue on the corporate network after all. It only involves hacking into the server from the intranet and then entering the IP address to get onto the site.

The software supplier agrees with my diagnosis:

"They do like passing the buck, don't they? They've been fiddling with the network again."

"Can you have a chat with them again? They don't believe me."

"Will do."

I'm now debating whether or not to put the instructions for connection on the intranet...