Samsung TV Repair

Mode not supported message has come up on our 60 inch samsung TV when we try to use our blu ray player - which we use for everything. It has never done this in a year of using it. But the TV is old and was second hand when we got it. A couple of days after this the tv connected to the blu ray player and worked fine, then when it was turned off and back on again later it played programmes but flashed on and off and the sound kept cutting out. Now it's gone back to mode not supported. We have tried various HDMI cables to no avail and have tried changing the settings on our tv and blu ray player and nothing has worked so far.