playbook with dynamic variable interpolation doesn't work in ansible tower v2.4.5, any help with this?

[r...@telnyx.com]

reference: http://docs.ansible.com/ansible/faq.html#when-should-i-use-also-how-to-interpolate-variables-or-dynamic-variable-names

I have a playbook working fine via cli, however I am unable to figure why I cannot dynamically interpolate when running through tower. Statically is working fine.

I'm referencing the "vars" dict. to access data from a vars file via include_vars task.

vars['VALUE'] works to verify the data struct

vars[myvar | upper] does not. myvar being another variable set during the play.

any ideas?