Google Voice errors out on "Choose your number"

[restamp]

I'm helping a friend set up his OBI200.  We haven't even begun to configure the OBi yet, but are at the stage where we are selecting a Google Voice number. We've successfully linked his home phone with his google email account, but when we go to the next step of choosing a GV number and hit "Continue", Google shows a transient "Adding Google Voice Number" (in yellow), and then a fraction of a second later "There was an error with your request.  Please try again" (in pink) across the top of the "Choose your number" pseudo-popup screen.  Have tried several different numbers and tried the process from several different browsers with the same results.  Google hasn't asked us to re-register his home phone, so apparently that number remains linked with his account.

Any suggestions as to how to proceed?
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Addendum:  This problem looks suspiciously like the one described here:

https://productforums.google.com/forum/#!topic/voice/NjSbuJXMaNc

https://productforums.google.com/forum/#!topic/voice/YXhUZGnwzYw

However, the Google response differs in that it implies the error message should occur during the forwarding phone validation phase.  In our particular situation, like the original poster's, the error occurs after the forwarding phone has been approved and we are in the Google Voice number selection phase.

FWIW, our forwarding phone is a true landline phone, connected by twisted pair to the AT&T entity that serves our area, so I would think it would pass Google's litmus test.

[SteveInWA]

Follow Red's advice in the first thread you linked.  Try using a different forwarding number.  The one you are using is not eligible.

[restamp]

This evening, we tried registering with his cell phone and that worked.  It's difficult for me to conceive why Google would consider a true-blue twisted-pair account with an "AT&T" RBOC -- one which has been in service longer than Google has been in existence -- to be suspect, while accepting a cheap pay-as-you-go cell plan without reservation.  I also wish the error message could more clearly explain the problem, not so much for me, but for those without access to resources like this forum, who must truly be befuddled by such a failure.  But I suppose I shouldn't look a gift horse in the mouth.  Steve, thanks for the response.

The other thing worth pointing out from this adventure is that Google verifying ownership (or at least access) to a forwarding number (by requiring you to enter a few digits when called), is quite different from Google validating the number (ensuring it meets GV's litmus tests for being a number valid for use as a forwarding number which can be linked to your GV number).  The latter step is not performed until you actually attempt to link the forwarding number with the GV number you select.

BTW, does this mean that numbers assigned to VoIP services will no longer pass GV's more stringent validity checks?  (Does anyone know?)

[SteveInWA]

This evening, we tried registering with his cell phone and that worked.  It's difficult for me to conceive why Google would consider a true-blue twisted-pair account with an "AT&T" RBOC -- one which has been in service longer than Google has been in existence -- to be suspect, while accepting a cheap pay-as-you-go cell plan without reservation.  I also wish the error message could more clearly explain the problem, not so much for me, but for those without access to resources like this forum, who must truly be befuddled by such a failure.  But I suppose I shouldn't look a gift horse in the mouth.  Steve, thanks for the response.

The other thing worth pointing out from this adventure is that Google verifying ownership (or at least access) to a forwarding number (by requiring you to enter a few digits when called), is quite different from Google validating the number (ensuring it meets GV's litmus tests for being a number valid for use as a forwarding number which can be liked to your GV number).  The latter step is not performed until you actually attempt to link the forwarding number with the GV number you select.

BTW, does this mean that numbers assigned to VoIP services will no longer pass GV's more stringent validity checks?  (Does anyone know?)

These more-stringent requirements are anti-fraud measures.  I can't comment in any more detail, other than to acknowledge that new requirements are in place.