Apple TV maximum quantity in 1 network.

Hi Experts,

We had purchased 24 Apple TVs and setup in 1 network.

Recently, we found that one of the Apple TV is not in the list of Airplay of iPad Air 2.

We had done several methods include reset, re-configure and factory reset in iTunes but still in vain.

However, if I configure this Apple TV and the iPad Air 2 to another network, I can found it from the Airplay list and no problem on Airplay.

If I set back this Apple TV and iPad to the original network, I can't find it from Airplay list.

Are we had reached the maximum quantity of Apple TVs in 1 network?

If not, how to solve it?

Thanks,

Kenny.