Odd difference between local & remote version: if-statements not working online

I’m working with IF-statements (if is_single, is_archive, is_home, …) in the sidebar, and on the local version of the website (on my computer) this seems to work. The sidebar recognizes when it’s a single or archive page.

In the online version however, everything seems to considered as an archive page, eventhough the site-files are direct copies of the local version.

Have you got an idea what may be the problem here? Could it have something to do with online settings?

I’ve disabled all the pug-ins in order to find out if that could be the problem, but with no result.