Is your system fully updated?
Check also in the Software app if you have a update for the firmware to install.
Afterwards try to start the service by hand:
systemctl start iio-sensor-proxy.service #posting errors if you get some.
If this works afterwards you can enable the service so that it get started by system start.
systemctl enable iio-sensor-proxy.service #posting errors if you get some.
If everything not works, please have a look on this:
Inxi | the help to help your selves
If you do this on both machines you will have a good overview of the hardware and drivers you have in use.
The output of both, would then bee interesting for us, to help you.