Backup alerts not working (2019 CX-5)

The last couple of days, while backing into my garage, I have noticed that the side and rear alerts, notifying me when I'm getting close to the side or back walls, are not sounding. I have just noticed this, and don't yet know if other alerts -- like when I get too close to another car when turning into a parking space, lane departure, etc. -- are still working or not. Has anyone else had this issue? Anyone have a notion what the issue is? I have a 2019 CX-5 Signature, purchased new, 49K miles.
 
I know it's simple, but have you checked the switch by your left knee?
 
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