The issue is that Vapi is still treating the inbound INVITEs as Digest-authenticated instead of trusting the source IP, so it keeps replying with 401 Unauthorized even though your carrier only supports IP-auth mode. Since your carrier sends from 207.182.145.2 and the INVITEs are already reaching Vapi correctly, this usually means the IP hasn’t been added as a trusted inbound peer on Vapi’s side for your org. One quick question did you already whitelist 207.182.145.2 anywhere in the Vapi dashboard/backend, or is it only configured on the carrier side right now?