How do yox fix a olympus digital voice recorder VN-8500PC, it just reads please wait?

I will assume you are not plugging it into a computer when it is reading this? If you have it plugged into a computer, I'd eject it properly from the computer. The next thing I would try doing is replacing the batteries or making sure they are fully charged if you are using rechargeable batteries. If you are using a memory card in it, I'd pull the card out and see if it powers on properly without the card. If so, you might have a bad card or your card might need re-formatted. If none of the above work, I'd removed the batteries, push and hold the power button for 10 seconds, put the batteries back in and power it back on without any memory card in it and see if it is working.