Sounds like you might be editing the incorrect files, possibly you are editing files under /base/default when you should be editing under [your-package]/[your-theme].
Have you turned on template path hints and located the precise file? See Here
Also, another thing that can happen is if you’re editing files, say on a development server, and that magento install is hosted on the same server as the production site. Make sure you’re in the correct subdomain if that’s the case. It’s easy to get a little confused in cases like that and terribly frustrating when simple changes take much longer to do because of things like this.
Also, a good method to go by when you’re editing template files is to open up the file you think is the correct one, add a simple HTML comment near the top, and then upload/refresh the page. When you inspect the code, if you see your comment, you’re in the right place. Alternatively, you can add something like <h1>TEST!</h1> which should be visibly obvious if the changes were saved.
Hi - wondering did you ever get this sorted as I’m having the same problem. Cannot update my .phtml files or css files. I can rename a css file and upload it as a new one, but I can’t get it to recognise any changes after that, have to keep putting new ones up. And the .phtml files won’t recognise any changes either.
Am 100% sure that I’m changing the correct files and all caching is disabled.