Happy new year folks. Long overdue update but still no cigar...

Thanks to everybody above's input I now understand the fail problem comes from my gateway. I have tried the following steps:

Gateway (Arduino Uno) powered via USB by a high quality charger (iphone charger);
5V from Uno goes to an external down converter to get stable 3.3V;
Radio powered by 3.3V in parallel with 40 uF capacitor.

Sensor radio is also powered in parallel with 20 uF caps. I measured after all these steps I get 3.300 +/- 2 mV to the radio. Well problem solved or so I thought.

Only after these steps would I be able to get stable communication (verified by serial debug from the sensor), but it only lasts two hours max, after which I would get st=fail again until I unplug power to the gateway, replug it in and reload Vera.

Resetting gateway didn't help; simply reloading Vera didn't help. It had to be a hard reset by unplugging it. I am starting to suspect the radio I bought off eBay is from a bad batch (I bought a 5 pack but switching between them didn't help - they all communicate for a few minutes to 2 hours max then drop dead). Any ideas ? Thanks.

Honestly I'm not sure whether gateway problems would also lead to the sensor radio "st=fail" -- is that one of the reasons? Thanks.

For the sensor I have tried both 5V brick power supply to USB and just plugging in to the USB on my desktop computer;
for the gateway it's mostly on a 6V brick power supply, plugged directly to the power port on the Uno.

I will try debug mode on the gateway and see if there is a message.

Folks, I have benefited a lot from reading this forum but have to come up here to ask for one more help. This problem has baffled me for nearly 2 months:

Ethernet Gateway on VeraLite is made of a Uno with ethernet shield.

Problem is with a DHT22 sensor I am trying to make. The sensor radio is the correct NRF24L01+. Using a USB Arduino Nano. DHT22 code is working fine. But the radio keeps giving "st=fail" error, see below.

ensor started, id 1
send: 1-1-0-0 s=255,c=0,t=17,pt=0,l=3,st=fail:1.4
send: 1-1-0-0 s=255,c=3,t=6,pt=1,l=1,st=fail:0
send: 1-1-0-0 s=255,c=3,t=11,pt=0,l=8,st=fail:Humidity
send: 1-1-0-0 s=255,c=3,t=12,pt=0,l=3,st=fail:1.0
send: 1-1-0-0 s=0,c=0,t=7,pt=0,l=3,st=fail:1.4
send: 1-1-0-0 s=1,c=0,t=6,pt=0,l=3,st=fail:1.4
send: 1-1-0-0 s=1,c=1,t=0,pt=7,l=5,st=fail:74.3
send: 1-1-255-255 s=255,c=3,t=7,pt=0,l=0,st=fail:
T: 74.30
send: 1-1-0-0 s=0,c=1,t=1,pt=7,l=5,st=fail:55.8
H: 55.80
send: 1-1-0-0 s=0,c=1,t=1,pt=7,l=5,st=fail:55.5

Now every once in a couple weeks I will get "lucky" and get a few minutes of "st=ok" and connect to Vera successfully. But after a few minutes the data stream would just stop and when I checked debug on the sensor Arduino serial output it was "st=fail" again. I have put the radio power on the output of a 5 V to 3.3V regulator; have put 4.7uF and even 10uF capacitor across the radio power pins but kept seen the same results. Why didn't it work?