Not getting connected on Webmin login page is a common problem which has nothing to worry about. If there is an update to any of the software packages installed or Webmin modules it may happen. Another cause of inaccessible login page on Webmin may be a firewall that blocks any resources or newly installed/updated modules to work properly.
Restarting Webmin can enable you to access the login page on the browser. You can restart Webmin/ Virtualmin either by the restart command through SSH access using software like Putty or by rebooting the server. Rebooting the server is the easiest way to restart Webmin.
You can restart Webmin by rebooting the VPS - virtual private server
Using this below command you can restart Webmin through SSH
/etc/init.d/webmin restart