Stick up cam missing some motion

Installed two of these outside a few days ago. Worked well right away but last couple days are not catching all motion. I’ve increased sensitivity and still seems to be hit or miss. Any ideas on what else to do? Front one has missed vehicles in the driveway several times and rear one doesn’t seem to pick up anything today or yesterday...I just walked right by it and waved arms and circled several times and still nothing. ???? Defeats purpose if won’t pick up motion.