We (the Product Experts and Google staff on the Google Voice help forum) are getting sporadic reports of failures on OBiTALK devices. A recent inbound call failure was fixed. I have never seen a solution to reports of calls being disconnected after some time period.
Generally speaking, it isn't easy to diagnose the rather useless "has not received a response from the service provider" error. However, Google regularly suspends users' access to the service, when abuse is detected, which will cause that error. This is most commonly when people send many outbound text messages without an equivalent number of conversational replies, which looks like (and probably is) spam, or they make many outbound calls of rather short duration over a limited time period, which looks like (and probably is) robocalling or telemarketing. When this happens, the user will see a suspension notice when going to their Google Voice web page: https://voice.google.com/u/0/calls
My point about not using the mostly-free, consumer-class version of Google Voice for business, is that it is not supported at all for that purpose by Google, it occasionally breaks, and it might take hours or days to fix whatever might go wrong.
Google does have a paid, business-class version of Google Voice for G Suite customers. It includes direct support from Google, and it has a published service level. However, it does not work with 200 series, 1000 series, nor 2000 series products. It does work with newer Poly VVX IP phones.