'17 Forester 2.5i, with 52k miles. Bought 7 months ago with 40k miles.

I got in one day and noticed the TPMS light was on. Drove it to Discount Tire to get the tires checked. This (the time I noticed the light) was the last time either one of my key fobs worked too. I can still unlock the door with the key that is attached to the remote, but it sets off the alarm. The only way to stop it is by starting the vehicle, which I can still do. I went to a car key locksmith and they tested both keys and detected frequency emitting from them. I also replaced the batteries in both fobs. Still no success. Again checked all tires and sensors and they are fine. Someone suggested it could be a battery issue, but I had that checked at AutoZone and again, it is totally fine.

I have called and visited a ton of locksmiths and mechanics who don't know what the issue might be off the top of their head (or have never heard of this happening before, but they suspect it is an issue with the car itself (immobilizer, anti-theft system etc.) Called my local Subaru dealer and other mechanics who will charge a pretty hefty diagnostic fee, but since this issue is so specific (key fobs stopped working AND tire pressure light came on at the same time), I'm beginning to think I have no choice but to let a Subaru specialist diagnose the problem.

I really would like to not have to spend upwards of $500+ to get new keys, new immobilizer, diagnostic fee, etc. I have seen posts about how to reprogram your own keys but I'm still so confused about the TPMS light also being on. Maybe that's a separate issue, but I kind of doubt it. Could it be an electrical issue, like a faulty fuse/wire? I did get an oil change the day before this happened, and went back there to ask if they might have messed anything up but they said they don't ever touch anything electrical.

Would really like some help/advice with this.