Please ensure that you are using a test key when assigning your test URL in ACP -> System -> License Key. I looked on your license and your Test URL is indeed empty for Test URLs.
We recommend setting your test URL to a sub-domain of your Live URL's domain. That way, it's a simple DNS change to move an instance to a different server and there is no headache about what you're needing to do here.
While we are rather flexible with the Test URL system in terms of requests coming, it is setup to not let the client change it to avoid abuse of our policy. Thus, at current stage, this is not something which could be done and submitting a ticket is the only way to change your Test URL (no matter if your test installation actually exists or not).