That is a definite pain and disappointment.
On the very small plus side, no one else is taking your ADR by phone.
I was so frustrated by the website Sunday-Monday. I was trying to make an ADR for Crystal Palace. There were plenty of open slots for our time, but I kept getting a "server busy" "please log in" (um, how many times should I do that???) I was very concerned that I would lose our dream time (family of 7) by phone. Husband tried from his work computer and I turned off all the security on the computer. After 18 hours on and off, I got it booked and then the itinerary page was all funky. Showing us going every day of the week.
I hit the webpage feedback button at the bottom of the site and filed a complaint.
Just keep trying...Fingers crossed for you.