newly created Perch Content regions not appearing in Admin straight away

First off I'll say that I'm VERY new to Perch, so please excuse me if I miss name elements or fail to describe thing properly.

I have a copy of Perch (just upgraded to 3.1) on a remote web-hosting server... It's a bog-standard shared server platform, if that makes any odds. Perch is there purely for my own testing and learing.

I have an HTML page that I've converted into a PHP file. I added the relevant PHP include to the top of the file and saved the change... I went into Perch Admin and did a browser refresh - nothing appeared.

So I manually used the Add a Page button and filled in the details, pointing the page towards the URL of that relevant PHP file. All seemed fine and my page appeared.

I then went back to the PHP file and whipped away some text inside a pair of H1 tags and replaced it with a Perch Content tag with a unique "name".

I saved that updated PHP and went back into Perch Admin and did a browser refresh... The page did not gain any regions. I refreshed several times, I even cleared the cach and made Chrome do a Hard Reload. Still no region.

I've checked and double-checked that the content tag is correct, seems fine that I can tell. So why-oh-why is it failing to show up?

Thanks in advance, m.