Do you see something like this on your booking link or are the times never showing up? Also what sign in method are you using? 
Discussion
I get past that point. It's in the scheduling page where I need to enter a name, email and comment. The Book Event button was greyed out.
When I just checked this morning it's now clickable.
Initially I had set it to 21 sats, so if payments don't work it makes sense. I then changed it to 0 sat and it was still greyed out. Maybe it was just a delay in the relays updating the event to have no fee?
Ahh, got a few work buddies to try and book without having a nostr account, so they probably just need to be logged in to click submit for a time slot. When I did it this morning, I was logged into my account and I was able to book a time.
I think I have a fix coming in the next update push for this. If a user tries to book but isn't signed in the button will open the 'Login' modal to let them either Sign Up/Login and complete the booking. It should def help reduce that confusion point. Sat bookings still to come.