Nidec 4028 Fan

I have a Nidec fan it is connected and working properly. The tachometer reading I get is always 0 RPM (in red) even when the fan is running. This is how I have it in my config. Have I missed something?
pin: !fan_part_cooling_pin
cycle_time: 0.01
enable_pin: PA9
tachometer_pin: ^PD13
tachometer_poll_interval: 0.0005