Panel is offline

Virtualizor Service

If you are un-able to load panel then make sure virtualizor service is running which can be checked using :

service virtualizor status

If it is stopped then you will need to start the service.
If you use service virtualizor restart command then virtualizor will ping 4.2.2.1 . So if ping is disabled on your server then you can try starting php, nginx and mysql service separately :

/usr/local/emps/bin/fpmctl start
/usr/local/emps/bin/nginxctl start
/usr/local/emps/bin/mysqlctl start

Firewall

Virtualizor uses ports from 4081 - 4085. If there is any firewall restricting this, you will need to allow these ports.

For RHEL & CentOS < 7

iptables -I INPUT 1 -p tcp -m tcp --dport 4081:4085 -j ACCEPT

iptables -I INPUT 2 -p tcp -m tcp --dport 5900:6000 -j ACCEPT

For RHEL & CentOS 7+

firewall-cmd --zone=public --permanent --add-port=4081-4085/tcp

firewall-cmd --zone=public --permanent --add-port=5900-6000/tcp 

Mysql error

If you get this error while starting the service
'Starting MySQL.. ERROR! The server quit without updating PID file (/usr/local/emps/var/mysql/mysqld.pid). '
then make sure you have space on '/' partition.
You can check it using df -h command.

df -h

Filesystem Size Used Avail Use% Mounted on
/dev/md2   96G  96G  0G    100% /

If the space on '/' partition is 100% full then you will need to make space on that partition. Usually /var/virtualizor/ directory uses more space .

Logs

If the space is not full and you still receive the error message then you can check in logs stored under /usr/local/emps/var/log/ directory.
You can find logs for php, nginx and mysql under that directory.

Server offline

If you receive server is offline message on Master panel for any of your slave panel, then make sure that slave panel is working.
If there is firewall on slave then make sure you have added Master ip and allowed ports 4081-4085.
If that is not enough , you will need to cross-check Master ip and key on Master and Slave panel.