A couple things come to mind. First, is the storage card full? That can cause a problem when it is, which I inadvertently discovered. I had to put the SD card in my PC and delete the file in order to get it to work properly again.
And, as Donny asked, did you remove the battery? Sometimes, especially if the battery contacts become the least bit corroded, this can cause a problem because the voltage is below operational level.
Just a guess,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)