TPMS warning light flashes then stays on

[Hamster]

Hi everyone! Just had my first ever problem with my Yaris. But it's a minor one. I had new tires put on in May. No new rims or anything like that, just new tires. No issues. Then, today, six months later, my TPMS warning light came on. I expected this, since we just had the first hard frost of the year, and my tires always lose some PSI after the first hard frost. No heat in my detached garage, so it gets cold in there. Anyway, I put air in the tires, like I always do when this happens. No big deal, right? Except this time, the TPMS warning light wouldn't shut off, even after I drove 50 miles on the highway. Now, when I turn the car on, the TPMS warning light flashes several times then stays on, which the owner's manual indicates that there's a malfunction in the system. I did a search of this forum and read that sometimes this "malfunction" is simply that the batteries died in the TPMS sensors. Do you think this is the case? I've owned this car since new, and the TPMS sensors have the original batteries.

Or is this something I should just ignore? This car is over ten years old, so is this TPMS problem just a typical "old car" issue? I don't want to spend big $$$$ on fixing a nanny system. But on the other hand, if it's likely something simple and inexpensive to fix, I'll consider getting it fixed. Thanks everyone!