Help booking Delhi-Kota

Hi all-
I was hoping to take train #2952 on Dec. 5, from Delhi to Kota. Knowing this is a popular route (as it's the overnight to Mumbai), I looked it up as soon at it became available - but it showed "no availability" on 1A. Same happened for the following days.
Can anyone explain this? Did it just sell out immediately? Or are the 1A seats held for "through" passengers (ie going all the way to Mumbai), or did the booking window go back to 60 days, or is there some other reason? There are 2 2A seats open, so perhaps I should take those while I can.
This is my first try at booking online, so apologies if I've missed something obvious here.
Thanks!

Take the 2A (or 3A) seats, I'm surprised you could book any class for such a short distance on this premier trains.

Thanks for your help Steven! I've booked what appear to be the only 2A seats available on this route. I guess they hold the premier seats for folks going a lot further than we are. (Though I did notice 2 1A seats available under the tourist quote, but not going to take that chance.)