If you are using CSF firewall and by any chance you are having team viewer installed on that server to in order to get team viewer running fine and get the id and password you need to allow the port “5938” in your CSF configuration.
Unfinished Stories of an Expat in M̶a̶l̶a̶y̶s̶i̶a̶ Germany
CSF: refers to Config Security Firewall which is a Firewall Application for Linux Servers.