Telnet is not recognized as internal or external command
You have to go to Control Panel>Programs>Turn Windows features on or off. Then, check "Telnet Client" and save the changes. You might have to wait about a few minutes before the change could take effect.
- Open "Start" (Windows Button)
- Search for "Turn Windows features On or Off"
- Check "Telnet client" and check "Telnet server".
You can also try dism /online /Enable-Feature /FeatureName:TelnetClient
Run this command with "Run as an administrator"
Reference