Key fob won't lock/unlock 2006 hhr- tried 4 different batteries in fob
 

Yesterday my stepdad went under my hood to check fluids and such, not sure what else he touched under there (he's a mechanic and idk if he was looking around). Anywho, immediately after he was done, I grabbed my keys to go to the store, and they fob wouldn't unlock the car. I changed the battery 4 times (each time, a new battery). Not sure what could be the issue. Where is the key fob receiver in an 06 HHR? This has never happened before, and never, not once, did the fob show signs of weak battery and worked 100% of the times I've used it prior to my stepdad going under the hood. (Also, my interior fuse box is exposed, as the passenger side panel was knocked off - idk if a fuse in there acts as a receiver of the fob)

The fuse to the receiver is in there , perhaps loose or burnt.

Love how you use idk (I don't Know) but type out the rest.
If the inside panel is off and your step dad was doing things I would ask him first.
#26 is the location for the door lock fuse on the panel inside the car.
If you have a manual, look up fuses in the index of it to show its location.

Why not ask your stepdad, the mechanic, what he could have done under there ?
I would assume he used the fob to unlock the car to get to the hood latch. Also, I would assume he used the fob to lock the car back since it was locked when you tried the fob.
Yes. Start with questioning him. Maybe he dropped the fob (broke something in it ) after locking the car.

It's possible that the car battery is dead. Your nearest auto parts store may perform a load test for free.

I tried asking my stepdad, but he has this ego thing where if you suggest he might've made any kind of mistake, he shuts down and doesn't answer your questions. He got kind of defensive and didn't help me solve the issue or answer questions as to what else he did in my car. So that's why I'm in this forum.
the battery isn't dead, my car runs perfectly. The power lock button on my driver door works, just the key fob doesn't even with brand new batteries

yes he did unlock my car to open the hood, but not to lock it afterwards, because my car was unlocked after he finishes doing whatever he did

Please read #3 post.
Also time for your mother to get thru to him.
Don't let him work on the car again.

The fobs are notorius for the battery holder to come unsoldered.

Endless thank-yous to all of you for your input! I located fuse #26 in my interior panel fuse box, pushed it in, and now my fob works! Thanks again! 🙏🏼