Restore SharePoint EditForm to Default

[JosWhite]

Hi all,

I've started migrating from a classic environment to a modern environment in SharePoint. This includes redesigning InfoPath forms into PowerApps. All is well in the actual power app however when I go to the SharePoint list it is still wanting to use the old InfoPath form.

I've already gone into List Settings > Form Settings and changed it over to the PowerApps form:

When I open an item using the EditForm.aspx it brings up a blank page as if there is no web part for the PowerApp. The page itself is reminiscent of the old classic page so I would believe it needs reset to show the modern page with the PowerApp form embedded.

What I've tried so far (keeping in mind that I am not only in the Owners group but also a Site Collection Admin):

1. Under the InfoPath section, Delete custom form. Don't do that. It wipes out the new and edit form pages which do not get automatically recreated. 
2. Change to "Use the default SharePoint form" and then re-publish the PowerApp. Did not change the EditForm.aspx page at all.
3. Created a new list on the same site - has the new EditForm.aspx with the PowerApp embedded.
4. Tried browsing the site to manually in Windows Explorer to edit the aspx file to add the code for the PowerApp web part - access denied.
5. Tried opening the site in old SharePoint Designer 2013 to edit the aspx file - access denied.
6. Tried copying the EditForm.aspx file from the working list to the non-working list - access denied.

Oddly enough with all of the access denied, I am able to copy the aspx file over as a .txt file. I just cannot rename it to .aspx. 

The NewForm.aspx page is also doing the same behavior however when making a new item in the list it pops out in the side drawer so it's not as worrisome. Most of my Flows link back to the EditForm.aspx form directly for the user to edit that specific item so I do need a solution to make this work. Any ideas?