Thanks for checking it out.
I do have a redirect plugin. I disabled it as you mentioned but then the site produced a white/blank page with the message “error” on it. I couldn’t get back into Admin. I just restored the database from a backup I had made just in case and had the site back running.
I’m using a plugin so I can have .html as link extension. I disabled this plugin, renamed the .htaccess and then reset the permalinks. So after this it worked as long as I didn’t use .html at the end of a link. But now links with .html extension didn’t work, giving me a 404 page.
I’ve changed this back as they were before since that way only one link gives me a 404 error. I just might remove the plugin which allows me to use .html, once I have more time, and then make sure to remove all .html extensions.
I’ll mark this as resolved.
Again, thanks for your help.