Forwarding calls to external numbers

I’ve set call forwarding from an extension to a external number and I’ve also tried by creating a ring group with an external number in the ring group. I put an “#” at the end of the external number as I read this suggestion.

If I dial the ring group or the extension with the forwarding from an extension, it forwards the call externally no problems.

However if I call the extension/ring group from outside using a DID and an inbound route, the call goes to voice mail straight away and does not forward the call. The CDR log report shows that the call was “not answered” even though the receiving phone did not even ring.

What I’m trying to achieve is external caller --> PBX —> cell phone
What works is internal caller --> PBX --> cell phone