Apple Watch series 5 does not stay paired to iPhone

My Apple Watch series 5 does not stay paired to my iPhone. My series 2 used to stay paired and re-pair when I came within Bluetooth range automatically, every time. This helped if I misplaced my iPhone, etc. The series 5 does not do this automatically. Anyone know why? Or how to correct this? It’s really a hassle to not get texts or know I have a phone call, etc.