Finally got it to work. On my phone, I got all the way through to the "Reserve" button again, but continued getting the "Oops" message. I was getting pissed, so I just kept hitting "Reserve" over and over and over again despite the error popping up -- after almost three dozen tries, it finally successfully went through and confirmed my reservation for the 30th at 1pm. So for anyone still struggling, brute forcing your way through that reservation button out of sheer anger might be the way to go.