Plex/ Alexa/ Amazon Fire TV Stick

Hi all,

Sorry if this question has already been asked. Im trying to get my 2 Fire Sticks working with my Amazon Dot. I thought the process would be easy but it appears not to be. My Fire Stick is running s/v Fire OS 5.2.4.1 and FireTV Home version 5.7.3-17. When I ask Alexa to open plex I get only the option for the chrome web browser not either of my firesticks. Looking at the supported listed of devices I can see that FireStick is listed.

Am I missing something very simple?

Thanks
Neil