Loopback of TX and RX in AD9361

Hi i am using ARRADIO and cyclone v soc.

I am running no os driver. When i set TX attenuation and feed modulated signal from other source my demodulator works fine

Then i removed other source and set tx attenuation to 10dB and feed to RX port(loopback). It does not work. What may be the reason?

I am searched all possible cause but could not succeeded.