I recently got the error code indicating an evaporative gas tank issue.... I ordered the Gates # 31832 cap and carefully walked the rubber seal off of the New Cap and carefully worked it back on my Old cap . Seems to work well.....
Just an fyi
Do you have a part number for the one you bought at NAPA?
I have the non-threaded type, part number THM 7031628. They also list a threaded type part number THM 7031719 that's a lot cheaper. Figures.