EX6400 / AC1900 WiFi Extender Connection Strength to Mobile Device

I just purchased a Netgear Model EX6400 "AC1900 WiFi Range Extender". Where I have it located (plugged in), I get a strong connection to my existing provider-supplied router (green light on solid). However, I'm only getting a solid amber light for the "Client Link" LED. I only have three mobil devices hooked up to the extender and even if all three are located 5 feet from the extender, I still only get an amber light (instead of green). Anyone have an explanation?