The backup sensory (proximity) sensors stopped working (no beeps). on 2009 Toyota Camry

What's the common cause for backup sensors to stop working? Seems like it stopped giving me the first beeps and now no beeps at all. Just stopped working. Fuse? Wiring loose? A bad sensor? And where do I take it to be fixed besides the dealer in Jacksonville, Florida? Thanks in advance for answers.

Asked by for the 2009 Toyota Camry