Coordinator can't find routers

We have a coordinator XBIB-U_dev in front of 2 routers XBee Pro52B - 30 cm - but it can’t find them
If we set the routers like a end device everything is ok
I must use 1 coordinator with 2 routers and 9 end devices
Someone can help me please ?
Thank you

What firmware versions are you working with? What settings are you using?