If you are encountering 404 error pages there are a few things it could be. You should try the following in order:

  1. 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.
  2. 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.
  3. 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.