I am also facing the same thing right now, What I found about the NGINX 404 Error is that we can successfully send the request to the website but the specific file cannot be found on the server. Even this is due to a misconfiguration of the server.
Let's wait for the NotATether reply :")
Edited: Maybe this is the reason?
I am investigating a configuration error in the shared backend server.
Thank you for your patience.
The tool now works though the data seems to be a little off. Earlier on i thought the mempool was nearly empty but in reality it is not thanks to what Cricktor
pointed out. Maybe it could be related to the error NotATether talked about yesterday.