Ubiquiti changed up their download pages and it appears that there is not a page to download the AirGateway Pro firmware.
The normal AirGateway and AirGateway LR use the same firmware. The Pro can use either 2.4 or 5Ghz frequencies and has a different firmware download.
When we search for AirGateway, we only find results for the regular and LR.
There is also no download link on either AirGateway page for the Pro.
Fortunately, we can copy the download link, and change the firmware name to download the Pro version. All we need to do is change “AirGW” to “AirGWP”
Here is the direct link.