Catastrophic ProctorU experience on Macbook

Has anyone else been unable to complete the Argumentative Writing portion?

I tried to connect for 2+ hours today. I have a MacBook Air which meets all the required specs, downloaded the newest OS, updated Chrome as advised, and downloaded the Guardian extension. But when I clicked the test link, it took me to a page to download the Guardian extension again as if it wasn't already there. No matter what I did, I never got past this page.

Numerous calls to tech support were useless, I was advised to do the same few things over and over before they ultimately opened a new tab to connect me to a proctor and rapidly disconnected the chat. Restart computer. Remove and add Guardian extension. Uninstall and reinstall Chrome. Lather, rinse, repeat. The prevailing advice from LSAC, because this is a novel issue, was to "try another computer." Not really a feasible option for me, so I tried going the Apple support route with no success. Then LSAC advised me on the last call this is a "known issue" and to try again in a few days.

At this point I'm beyond frustrated and at a loss. Has anyone else experienced this? If so, how did you fix it?