I have removed all of the bolts on the valve cover. Something won't allow it to come off. I have a '97 Cadillac DeVille. Can any one offer a solution?

I have removed all of the bolts on the valve cover. Something wont allow it to come off. I have a '97 Cadillac DeVille. Can any one offer a solution?
Front valve cover?
The water pump on your NorthStar is driven by the intake cam.
You've gotten yourself into a serious pickle with this one.
You first need to remove the water pump belt, etc. and have the drive pulley removed with the proper pulley puller. Once that is done, remove the seal from that end (never reinstall that seal-replace with new). You will need the correct tool to reinstall that drive pulley once the new valve cover/valve cover gasket is installed.
Once that is all done, you can remove the valve cover. Always recommended during this repair: new water pump belt and water pump belt tensioner. And if you haven't replaced the water pump recently, this may be a good time.