Hi @Sundar Thulasiraman ,
Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.
From the information you provided we understand that you are facing an issue while trying to open the Linux VM through CLI.
Please re-confirm that you are trying to open it with the same password and username with which you deployed the VM.
Please check if you have enabled port number 22 for SSH at NSG. If not, add port number 22.
Please whitelist your ISP IP address at NSG.
Try to reconnect with CLI again.
If you have any further queries, do let us know.
If the answer is helpful, please click "Accept Answer" and "Upvote it."