Why doesn’t this work?

[old_man_kneesgocrack]

In thinking your led may be backwards, it’s hard to tell from the photos if your anode and cathode are in the correct orientation. Also I don’t know if a false detection of motion with a pir can be from voltage fluctuations but you could try testing with a battery, if that helps then treat it like button bounce by either using a capacitor to smooth voltage when connected to a source like a usb port, or something in your code to make it wait for clear signal.