Does your VoIP device buzz or hum?

Is there buzz or hum or noise on the line?

The solution is probably easier than you might think:

Move your device away from any electrical device near to it, especially AC/DC converters.

That's what worked for my Vonage box.

While I was looking for info I also found info that just plugging another phone into line 2, a non-working line 2, got rid of the noise.