Got this working. the appropriate spells and incantations are from this older post:
http://forum.mikrotik.com/t/solved-capsman-wap-ac-5ghz-no-supported-band-united-states-3/111709/1
and here is my reply summarizing the results to another:
http://forum.mikrotik.com/t/capsman-5ghz/121104/1
The part I was missing is the need to set up channel selections. And you need to set up configurations that select those channels. Finally, you need to set up provisioning so that hardware modes are selected.