av sender

for the past 9 months i have been useing an av-link compact 2.4 av transmission system,i am on sky,this has worked perfect ,i could go to my room and watch whatever program i wanted ,but this week for no reason i can only watch what is running on the main sky box,i cant change channels on my own set ,now the picture is perfect so i am assuming that there is no fault with the sender and the volum controls work,so would anyone have any suggestions as to what is causing this fault,at this stage i have no hair to pull out.