Why not remove/delete the certificate and issue a new one? See the reply that I marked as the solution here: "Certbot failed to authenticate some domains (authenticator: nginx)" - #14 by pxfreelance
I had this same issue and stumbled on your post before I ever had to create mine. Everything seemed to fail and that was my last resort and it worked for me. You could try that since the certificate hasn't expired yet. Mine already expired at the time and all attempts to renew failed.