When you run Connect-NsxtServer in the PowerCLI, it may show "Unable to connect to the remote server".
Because the error message is a little bit confusing with other login issues. It's not easy to troubleshoot. The actual reason is the NSX-T uses a self-signed certificate, and the PowerCLI cannot accept the certificate automatically.
The fix is super easy. You need to set the PowerCLI to ignore the invalid certificate with the following command:
Set-PowerCLIConfiguration -Scope User -InvalidCertificateAction:Ignore -Confirm:$false