Touchscreen button to move sound back to front is unresponsive

My daughter's 2015 Prius C started having an unusual issue, where the touchscreen buttons along the bottom edge of the display (pictured) seem to no longer respond to touch. There aren't any other problems, or screen discoloration, etc. This just seemed to start a few days ago.

For what it's worth, she says the main issue is she'd really like to move the sound from back of the the car to the front.

If anyone has some insights here, I'd be very grateful to hear. Thanks in advance!

 

Follow up, sort of good news: my daughter reported that today she was able to activate the Sound button as pictured, and the immediate need is taken care off. I verified yesterday it was not working. Perhaps it's just a lucky confluence today of favorable electric/static conditions.

Anyway, it turned out to be a temporary condition.