Yes it's the drain error, and no you shouldn't buy a new pump until you've determined you need one.

You'll need to drain it completely somehow. Behind that bottom panel is a pump clean out you can check once it is empty. I'd use a shopvac to suck it out but a large bucket under the large screw out piece can do it too. Be prepared for whatever water is inside to come out and try to do it in a controlled manner, slowly.. There's always some, no matter what you see.

Chances are you have something in the trap and you pump probably survives. The trap is the white screw out piece in the middle. Check youtube for guidance.

It sounds like you've covered all over the basics steps. If the pump is humming that means you know it is getting power and there's a possibility it is blocked by a bobby pin or something inside the pump chamber.
One final thing to check is that the pump is actually physically able to turn. You can do this by a couple of methods but the easy way is to stick your finger into the hole that the water goes into and see if you can physically turn the pump impeller.
Do that when it's off and empathy of course. The hole will be on the right leading over to the motor.
If you are really motivated you can pull the pump motor from the white plastic body by removing those three screws. If you can significantly wobble the impeller or show signs of damage you're going to need a new one.
They are not that expensive online. Probably $40 or so. You can't get the pump as a whole assembly or sometimes just the motor.
Have fun with it