Error calling tune on sub devices

Hello!
I am an undergraduate student and doing my project on USRP and using
RFX900 for my work Transmitter is working perfectly but suddenly
Receiver stops working and the error message

“Error calling Tune on sub devices”

Kindly help me I have only 1 day and i am facing this issue.
Thanks in advance.

Regards :
Syed Muhammad Saad Ali