Your vendor is a freakin' idiot who doesn't understand the concept of "graceful degradation".
Please tell them I said so, and feel free to use more colorful metaphors (think Jersey truck stop).
Having said that, my suggestion is that you try to get Google Analytics unblocked -- it's by far the easiest solution, and probably no serious harm to your organization.
If you can't do that for Real Valid Policy Reasons ("It's SIPRNet you fool!") figure out what their app is doing -- unblock Google Analytics for a few minutes (or test outside your firewall) to see what it's hitting and what GA responds with, then mock up a server that always returns something the app considers a "valid" response.
You'll need to modify your proxy/DNS/firewall/something to send Google Analytics traffic to this internal page (make sure you document this hack), but it should work, until/unless Google changes what Analytics returns and AutoDesk changes what they expect to see.
Your maintenance mileage may vary -- this is obviously not a solution AutoDesk is going to support, and we can only offer you limited help with it as it's generally a Bad Thing to do...