If a BYOC Premises Edge appliance fails, does IVR continue to work with N+1?

Yes. Redundant BYOC Premises Edges allow for IVR calls to be received after the active Edge in an N+1 Edge arrangement fails.
Each Edge device in a BYOC Premises Edge group has access to every configured IVR. In the case of a single BYOC Premises Edge failure, IVR calls will route to one of the other Edges in the group to service the IVR call.