If you are encountering 404 error pages there are a few things it could be. You should try the following in order:
- Most likely it’s permalink issue. You can fix it by by going to Settings > Permalinks from your WordPress dashboard and pressing the “Save” button without changing anything.
- If that didn’t work try disabling other installed plugins and then repeating step one. If it is a plugin conflict you can then either leave the problem plugin disabled or contact the author for assistance.
- Switch to a default theme (like Twenty Twenty) to rule out a conflict, again repeating step one after doing so.
By this point most problems should have been identified.