I went through the cake screen and into name/payment etc so it seems like it would work if I wanted to make the reservation. This is so strange!!
Just searched again, and the app shows no availability on 9/2, 9/9, 9/16, and 9/30, but it again showed the times for 9/23.
And tried my DH’s app, and he got the same message you did-no availability. ????