You need to update Ubuntu and restart the server.
This is an empty request and doesn't interfere with the server.
Make sure that a private key was formated to HEX. A correct private key in HEX-format starts from "307" beside "0x" in the beginning.
The page for validation private key - http://testpage.metahash.org/privete_key_validator.php
Make sure that this server have enough RPS/QPS. Minimum for it - 2000.
Updated about 4 years ago