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wait a few mins and see if you get a confirmation email... mine timed out when i selected the time to continue and i had to type in my apple ID and PW...but i got a confirmation email... 2 to be exact

This. I got two confirmations from the two different times I added. I will cancel one. If you get the "service unavailable" and your time is gone when you go back in, wait for the confirmation email. Mine took about 5 minutes to come.
 
Now I have 2 email confirmations and 2 reservations for the same time. I figured out where to view them -- Click the Reschedule/Cancel link in the emails.

Good tip. I see I have two reservations for the same time and place, thanks to the numerous tries I took on the crashy overloaded site. Oh, swell.
 
If it errors out, you still might have made an appointment. I got tons of errors but eventually it said no more reservations for me since I booked three already.... I canceled one then it errored out. I can't figure out how to view the ones I did schedule to confirm the time and cancel one. What a mess.
 
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