Motion Sensor Exclamation Point when "Adding" and then won't stop "Detecting"

I’m trying to set up my home security system. Everything works except one motion detector. When I add it, I get a brief, red exclamation point on my phone screen which promptly disappears. I go ahead with the addition, it shows up as one of my sensors but then, it continually shows red, continuous motion detection. It never goes to “Clear.”

I’ve deleted and reinstalled it several times. Same result.