Having trouble editing php files with latest theme update

I need to add a small div of text in my header and footer and whenever I save the change, it doesn’t show up on the actual site itself. Searching within the source code of the updated site does not reveal my specific div ID. Is there something I’m missing out on? When I save the php file, all my changes are there, but nothing appears in the actual site itself. Have checked on different computers/phones to see if it was a caching issue but that’s definitely not the case.