Try to use a paint key, not a screwdriver. If the lid is still stuck, hammer the plug back into place and try prying it again. If that still doesn’t work, strike the plug dead center and it will release, every time.
Here is a video illustration of that process:
Listen for the POP when the plug releases. This works for gallons and quarts, ¼ pints might need a smaller hammer but will have the same result. The best part is, the plug will have a dent in it, but still be useable. Just hammer the dented plug back into place to seal the can.
When opening and closing the lid of a can of any paint, some of the coating can get on the rim. Rust Bullet has such amazing adhesion qualities, that it will literally glue the lid to the rim. It will happen more often with the smaller cans. Take care to wipe clean the rim of your can before resealing, or use a piece of plastic wrap to create a barrier between the can and lid before resealing.