If you are still experiencing this, can you please try to go to your Admin Panel and navigate to ‘Settings’ > ‘Permalinks’ and just click the ‘Save Changes’ button without doing anything? Then please let me know if the issue persists.
The above procedure is known as ‘flushing permalinks’ and is a common cure for 404 errors in WordPress.
Please excuse the late reply. I’ll be getting back to you sooner from now on.