Cam playback rarely works

So… camera is only about 3 months old or so and live feed on my phone is great but the playback feature doesn’t work any more. I can back up the time but the Play button doesn’t do anything and the image just sits there. Kinda pissing me off. Twice now I haven’t been able to go back and record events that are pretty important and the reason I bought the damn thing. I do have a hefty SD card in there.