Unable to create new site page using flow

Hello,

We have  a powerapp/flow combo that allows users to fill out a brief form in powerapps, and it creates a modern page for them with the appropriate metadata etc in our sitepages folder. It works very well on our hub site, but recently I wanted to expand it so that users could also use it for sites that were associated with that hub site.

But when the flow hits "Create a file" in the associated sites site pages folder it says 403 permission denied even though I have full control of that folder. Is there something about a .aspx file content that means it can't be transferred to another site?