I'm hoping someone can advise me with a 404 error on WordPress when I create a new portfolio or page to add new work to my website.

When I create a new portfolio or page and I click on any of the columns under "portfolio page settings" or "page settings" instead of the column opening up, I get redirected to my website and a 404 error message saying "we couldn't find the page you were looking for" appears.

This has been happening for a couple of months now. Everything is up date including the PHP and we've done everything our provider has suggested but it's still not fixed.

I contacted a WordPress forum and they suggested it sounds like an issue with a plugin or a theme and to contact the support from those instead so I'm hoping you can advise.

Thanks!