As most people know by now, Google has changed Google Voice from xmpp to a proprietary flavor of SIP and, as a result, MOTIF no longer works within FreePBX. If you are still connected via MOTIF, you’ll be able to call out, but you won’t be able to hear your callers, though they can hear you.
There is a third-party solution using GVSIP here: How-To Guide for Google Voice with Freepbx 14 & asterisk gvsip, Ubuntu 18.04
However, the simplest way to maintain Google Voice is through use of an OBiHi OBi200. These are currently $49 at Amazon: https://www.amazon.com/OBi200-1-Port-Adapter-Support-Service/dp/B00BUV7C9A/ref=sr_1_1?ie=UTF8&qid=1532897616&sr=8-1&keywords=obi200
OBiHi has an agreement with Google and can accurately and easily connect to Google Voice accounts.
There are instructions for setting up an OBi200 (or 220) to work with FreePBX here: http://nerdvittles.com/?p=25846
These instructions are for use with IncrediblePBX, but they will work with FreePBX.
A couple of points:
The instructions are for configuring the Obi200 through the dashboard at obitalk.com. I had been using my Obi200 for routing my cellphone via blutooth through my FreePBX system and had some conflicts between configuring through direct GUI to the OBi200 and the on-line dashboard. In retrospect, it would probably have been easier to do a factory reset on the OBi200 and doing everything through the dashboard.
The only way to connect the Obi200 to Google Voice is through the on-line dashboard. However, it is very, very simple and very quick.
I’m not sure whether it’s Google Voice, the Obi200 or a combination of both but, whereas the Google Voice DID formally included a leading 1, i.e. 15559871234, now it does not, i.e. 5559871234. You’ll have to adjust your inbound route accordingly.
Making configuration changes via the on-line dashboard do not always “take.” Sometimes, you’ll need to make changes multiple times. It’s also advisable to re-boot the OBi200 after you’ve set up the configuration through the on-line dashboard, as the OBi200 seems to get its settings from the OBitalk site every time it reboots.
The OBi200 will support 2 separate Google Voice accounts and can be configured to be seen as two different trunks on FreePBX. I’ve got mine set up with two separate accounts. You can also use multiple OBi200s if you want to configure more than 2 Google Voice accounts.
I’d recommend that, rather than trying to modify either the old MOTIF Google Voice trunk and inbound and outbound routes in FreePBX, delete them and create new ones fresh.
That’s about it. Given the low cost of the OBi200, I think it makes more sense to use that, than to try the GVSIP mods to Asterisk and FreePBX if you have a home or small-office system. Of course, if you’re running a large system, $49 extra per trunk could be prohibitive.
I hope this helps.