A 404 error, also known as a “Page Not Found” error, indicates that your browser can’t locate the page you’re trying to access. Follow these 2 steps in order and check if the error has been resolved.
1. Change Your WordPress Permalinks
Start by navigating to your Settings > Permalinks tab. Select the Plain option and click on the Save button at the bottom of the page.
The page will reload. Now go ahead and visit your website as you normally would. Examine the pages that previously produced WordPress 404 errors to check if it remains error.
2. Disable Your WordPress Themes and Plugins
Sometimes your plugins and themes can affect your WordPress URL structure, depending on their settings. Plugins, in particular, can sometimes have bugs or compatibility issues that prevent a site from loading. To get started, head to your WordPress dashboard and navigate to Plugins > Installed Plugins.
Click on the Deactivate button below the first plugin. You can see that active plugins are shaded blue, while those that are off are white.