Putty not able to logged in, but on I can SSH through ESXi console [closed]

I'm stuck in having access to a server of my client via Putty

I'm running a Ubuntu 20.04 server

When I want to login, it always shows this error

Permission Denied

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But when I try to login SSH within the server (VM on VMware ESXi) itself, it's accessible

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I've tried to do AllowUsers to enable my user to ssh with their designated username but the server still refuses the conenct. I believe the internet allowed SSH at their firewall.

Have gone through some similar issues but quite not understand what should I do.