Dan has you on the right track on this. Let me add further insight.
First, in kitchen slide, there are a number of AC circuits (regular outlets, some GFCI protected outlets, fireplace outlet, microwave outlet and refrigerator outlet). I'll assume that what's not working for you are the
regular outlets (entertainment center and possible an outlet under the upper cabinet by the stove).
It is my understanding, that generally, the wire path for the regular outlets in the Landmark are as follows:
Branch circuit breaker > junction box on door-side frame below door-side slide
From junction box > back into frame and back to rear wall outlets
From last rear wall outlet > back into frame
From frame > junction box on off-door-side frame
From junction box > up into off-door-side slide
So that is your probably wire path. Like Dan, I'm guessing, based on your observation, that you have an electrical discontinuity in the junction box under the kitchen slide on the frame.
That said, be aware that there are many junction boxes there. One for possibly each of the different circuits mentioned above.
Once, I lost power to all of my
regular outlets in both the downstairs slide and the back wall. After speaking to the plant on the wire path, I knew to check the junction box under my door-side slide as that's the first connection point after the branch circuit breaker. Since you don't mention loss of power to regular outlets in the door-side slide - this is why we're encouraging you to start on the off-door side slide.
Hope this wasn't too much info. Just trying to paint a picture for you
And of course, if electrical is not your thing, stay safe and leave it to a pro.