If your server is unreachable check these things first:
- Does the panel say its offline? If it is offline then then try to boot it.
- If the panel says its online then use the panel's VNC connection to see it has actually finished booting or to see any other errors.
- Sometimes when viewing your VPS through VNC it might indicate filesystem errors. You may need to run fsck on the system to fix the errors.
If you have checked these things and still the server is unreachable then submit a support ticket.