Satellite positions wont store on receiver

When I got up yesterday morning the receiver was on standby, strange as I had left it on the night before. When I turned it on i had no signal in the bar on 28. I moved it round to 19 and still no signal. I then sent it back to 28 and it went passed the sat. So i went to set up, red button tune, selected a frequency and fine tuned until I got a strong signal and picture. Scrolled down Green button and stored. When I changed satellite and came back to 28 the same thing happened. I have tried to store it but it wont. Any help as to why will be most gratefull