This is just in front of the wheel well where the underbody shield meets the frame. Looks like there should be a fastener there? Missing on both sides. There is a bolt about 10” inboard of this. Anyone else missing this fastener or not? Two week old car.
Yep, I noticed that on my new M3P- as well. When the mobile service tech came to my house to perform some other minor warranty work, I showed him the two areas you mention, and he put new retaining clips in them. Still not clear to me if Tesla intended clips in these two locations, but the mobile technician felt they should have the plastic retainers.
Not unusual. These are simple plastic push pins, that if not installed properly can fall out.
Imagine Service center will replace them, or just give you a handfull for a DIY fix. These push pins are a common item on most all modern cars. They have a center piece that you push in with your finger and it locks into place.
If you are not near a service center, your local Dodge dealer will also, most likely, be able to get you some inexpensively. Perhaps also at Pep Boys etc.
The usually are not critical, but hold plastic trim pieces in place.
These plastic push-in clips are located literally everywhere throughout the vehicle... on interior door panels, trunk & frunk liners, exterior body panels, wheel well liners, etc....
Fortunately, a missing clip here or there is not going to harm anything or cause that particular panel/section to fall off.
The particular undercarriage panel shown in your photo (with the two missing push-in clips) is already held securely in place by other methods and at other locations. So, zero risk for this panel to fall off even without those two push-in clips.
I wouldn’t sweat looking for any other missing clips, but if want to check to just to be sure and put your mind at ease, then I would check the various clips that are visible along the four wheel well liners and perhaps under the front and rear bumper.