I've been struggling getting my work phone number verified with Google Voice. The way that number verification works is that Google Voice calls you and asks you to enter the two-digit code that's displayed on the website. But for some reason when I get a call on my outside line and I press a number button, it doesn't send that DTMF tone. Instead it tries to place another call.
My solution? I found a DTMF tone generator online and I played the code DTMF tones through my computer speakers.
It's nice to see that these old phone tricks still work.