Appreciate some help identyfying this snag

The original 3DR controller stopped working and I have replaced it with a Taranis Plus.

Using Iris with this setup Fr Sky D4R-II RX / Taranis Fr Sky DJT TX:  

When connected via Mavlink, Mission Planner shows the correct modes as selected on the Taranis - motors not running.

When Iris is armed with motors running and mode changes are made on the Taranis, Mission Planner does not show the correct mode.

Appreciate your help to identify what the problem is - Thanks Tim