External Number forward to IVR

I have a google voice number that I have forwarded to our office number, so when someone calls the google voice number they should get redirected to the IVR at the office number…problem is, if the inbound route on the PBX is set to an IVR prompt then the call just rings and rings. If I set the inbound route to an extension, the call will ring my desk… seems like it doesn’t like the IVR. Is there a way to get this to work? Thanks