Thanks so much for reaching out!
Do you see any difference in the connectivity on your phone, even if the device itself doesn't appear to be connecting?
I have the same issue today. I registered my T-mobile NXT Cel-Fi-D32-NU at the T-mobile website even though Amazon was supposed to do that as part of the purchase. So far, the green light just flashes. I have left it plugged in for hours because troubleshooting help suggests it may take 2 hours for it to fully connect. I have 2 bars and 4G on my phone in the spot where I am trying to set up the window unit. But so far no luck. I think the Window unit may be defective??