Pay Per Meeting Basic Plan Add-On Not Working

I am on the Basic plan and need to extend the time on a meeting I scheduled for Thursday.

I am trying to buy the "Pay per meeting" option.

When I click the "Buy Now" button, a pop-up appears. The popup is completely blank except for a blue button in the middle: "Take Survey" and underneath it "our survey takes about 2 minutes".

There is no option to buy. If I click the Take Survey button, another blank window appears and the only thing I can do there is click the X to exit.

So I end up nowhere. Thanks for your help!