What to do to get tender, edible steak instead of it being rubbery?
Starting with a "random piece of meat" may be part of the problem. Some cuts are more suitable for this than others.

If the meat seems "raw", then something is very wrong here. An hour at pressure-cooker temperatures is more than enough to over-cook it. There's no way it could be raw.

I suspect that over-cooking is the problem, and that will depend on the cut you're using. I suspect you've got a piece with little fat or connective tissue, and that's not going to soften in a pressure cooker. It shouldn't seem "raw", though; it should seem over-cooked.

In the future, I'd suggest looking for a chuck roast or other fatty piece. If you do end up with a cut like bottom round, it may help to cut it into thinner pieces, across the grain. That mechanically tenderizes the meat by snipping the chewy fibers.

Either that, or something is desperately, weirdly wrong with your pressure cooker.