Alright, chalk this up to beta testing mac OS software.
Answer
The FLS for the lookup had read only checked true.
Bug (I believe)
- The field or another field looking to the same object MUST be on the layout.....
Unfortunately the beta of the new mac OS hides the checkboxes so I could not tell it was set to true....
Doh!
Thanks sanket for your answer. It got me to do some serious digging knowing that you found it working......