My AC1753 Spare HDMI receiver does not work with my AC1752 sender

The AC1752 is a transmitter & receiver kit that lets you send HDMI over long distances using network cables. 

You can add additional receivers (AC1753 or AC1754) to use with AC1752, so that multiple receivers get the same HDMI signal from the original AC1752 sender - effectively making a video distribution network.

Which spare receiver you need to buy depends on the age of your original AC1752 kit, as these had a chipset update in 2021.

Older AC1752 kits will work with AC1753 spare receivers. 

Newer AC1752 kits will work with AC1754 spare receivers.

If you find that an AC1753 receiver will not work with your original AC1752 sender, you will need to swap it for an AC1754 receiver. 

There is no firmware update to make older AC1753 units compatible with newer AC1752 receivers, as they use different hardware.