I have an Obi202 with 2 lines (GVand Anveo). When I installed a PiHole on the network and pointed my desktop DNS to the PiHole instead of Google or Comcast, I immediately received a SIP disconnected warning email from Anveo. After resetting my desktop DNS to Google, I received an email from Anveo that the Obi's Anveo SIP has been restored.
I have not researched this further, but suspect that Anveo/Obi servers need to be added to the PiHole's exception list.