Getting the multiport option to "fit" correctly is most likely your problem. It is very hard to describe the proper method for attachment via a forum entry... but I'll try...
First if you look from the side and see any gaps between the option and the panel, the option is not seated correctly.
To seat correctly, I have found that you need to start the downward slide motion of the option "clicking" into place as close to the final position as possible... in other words, don't start the slide from the top.