Testing of a prototype does not work

EDIT: it suddenly works, and I did nothing differently, just retried again. This may be a bug. Has anyone else experienced this?

Not even the generic “First Project”. I tried refreshing, CTL+Shift + R… nada!
On the right hand side I see “new session started” - “new session ended”. When I click reset and test again, a message about needing to give microphone permissions pops up for 1/100th of a second and disappears again. I had to press over and over to even decipher this message, and there is nowhere in the settings where I can give permission, nor was I ever prompted to give it (bad UX!!), plus I should still be able to test via text input, but no box appears.

Help, please!

(Win 10, Chrome browser)