XBEE PRO S1 can send but cannot recieve RF data.

i have two XBEE PRO S1. I can send data from one XBEE to another XBEE. but i can not recieve from that XBEE!!! How can i correct this?

Thats pretty simpleā€¦ Set DH and DL of one xbee to SH and SL of another xbee and vice versa, provided both work in transparent mode (AP =0)