I got this error in HyperVM: "Could not Connect to the server localhost. Please login and restart hypervm" and i think one of the following actions may solve it:

a) restart hypervm by command: /script/restart

b) HyperVM / Server (tab) / Settings / as a "FQDN Hostname" set your server IP. Restart hypervm by command: /script/restart

c) check your server firewall and ensure it do not blocks itself ( or its public IP):
iptables -L INPUT --line-numbers|grep -E "DROP|REJECT"
If found such a rule you may try to remove it (if you realy want to and sure you can do it):
iptables -D INPUT LineNumberHere
If that does not solve issue, add the iptables rule again.
Restart hypervm by command: /script/restart