I have cleaned it a few times but I'm having a problem with removing the slide. I pull back then forward won't disengage. Any ideas.

Did you make sure you have rotated the sear deactivation lever?

From pg 21 of the Owner's Manual...

On my M&P 9's, I have found I have to take the following steps
1. Lock the slide back
2. Drop the sear deactivation lever (or pull the trigger later)
3. Rotate the slide removeal lever and hold it open (it wants to come back)
4. Release the slide and continue the motion forward. If I didn't do step 2, then I have to release the slide and then pull the trigger and then continue the motion forward.

Tg that was the problem thanks.

I just fixed that problem on my 9c. All you have to do is pull the lever out and you will see a molding burr on the take down pin. That burr catches on the recoil spring and makes the lever want to come back up.

About 10 seconds with a file and the burr is gone. It's really nice to have the lever stay where you put it!

You can search for the pictures, but it's really self explanatory once you pull out the take down pin.