Plesk interface is unresponsive;
The following error is shown in Plesk and in
PLESK_ERROR: 2017-11-24 05:14:40] ERR  Token validation failed: Can not connect to 'ka.plesk.com' (6:6). Please check connection to 'ka.plesk.com' or contact Plesk support: <a href='https://www.plesk.com/support/' target='_blank'>https://www.plesk.com/support/</a>.; ; KV network error (ka.plesk.com: cURL cannot communicate with license server https://ka.plesk.com:5224/jsonrest/pkp/20/verify-key (): Couldn't resolve host name(6)
Retrieving the license from CLI fails:
# plesk bin license --retrieve
Updating Plesk license key:
[2017-11-24 05:18:02] ERR [panel] KeyUpdate Result code: 2 Unspecified error
[2017-11-24 05:18:02] ERR [panel] KeyUpdate Result desc: License key is not prolongated yet
Telnet connection to ka.plesk.com works correctly:
# telnet ka.plesk.com 5224
Connected to ka.plesk.com.
Escape character is '^]'.
Running curl to ka.plesk.com:5224/jsonrest/pkp/20/verify-key works correctly. (Do not mind the error):
# curl https://ka.plesk.com:5224/jsonrest/pkp/20/verify-key
DNS records of ka.plesk.com cannot be resolved against some of the configured nameservers:
# cat /etc/resolv.conf
# dig @220.127.116.11 ka.plesk.com
;; connection timed out; no servers could be reached
DNS server misconfiguration.
1. Resolve the issue on the side of DNS server or remove the misconfigured DNS server from the interface settings.
2. Log in to the Plesk server via SSH and reinstall license key manually:
# plesk bin license --install A00000-A00000-A00000-A00000-A00000