have you tried to enable ssh , just to see if its a feature issue , shouldnt use telnet anyway , on new switches its all ssh by default , your running a k9 image so its supported crypto , much more secure
Global config
ip ssh time-out 120
ip ssh authentication-retries 3
ip ssh ver 2
ip domain-name ssh.com
then create the SSH keys with commands below in global config .....
crypto key generate rsa
Then hit return and tyep 2048 to generate an ssh version 2 key
Check its enabled with show ip ssh , should look like below
sh ip ssh
SSH Enabled - version 1.99
Authentication methods:publickey,keyboard-interactive,password
Authentication Publickey Algorithms:x509v3-ssh-rsa,ssh-rsa
Hostkey Algorithms:x509v3-ssh-rsa,ssh-rsa
Then use putty again but select ssh with port 22
if that works , turn off telnet on the VTY port by selecting input only as SSH
https://www.thegeekstuff.com/2013/08/enable-ssh-cisco/
