In Windows 2019 Standard telnet is disabled by default. To enable the telnet client on your Windows 2019 dedicated server open the command prompt and the run the following command:
dism /online /Enable-Feature /FeatureName:TelnetClient
If you are having trouble using telnet with your Windows 2019 dedicated server it might be because you have forgotten to enable telnet in your Windows settings.
It is usually a good idea to re-start Windows after you make any changes to its settings, this is also a good time to check if your dedicated server has any pending Windows updates that need to be installed.