Sometimes they can be hard to pull up even after the screw has been removed.
If you are sure there is not another screw holding it down take a needle noise pliers and take hold of it in the hole that the screw come out of.
Give it a good pull and it should break loose.
If you could post the full model number that is listed on the dishwasher model/serial number tag I could look up a diagram for it to see if it's just one screw that holds yours down.
The full model number should be something like 665.XXXXXX