Populate Word Template Flow not opening dotx files

Question

Hello,

Apologies in advance if this is a stupid question but I'm trying to create my first ever flow using the 'Populate a word template' step.

I've hit a brick wall as although I can access the sharepoint that the word template is stored on I can't 'see' it to open it. The only documents visible are docx ones (in the same SharePoint document library).

I'd appreciate any help because getting this to work would be amazing.