This is what I get when trying the same with PSTK 4.2 (latest version, just downloaded today)
PS C:\Users\admin> Connect-NaController -HTTPS server01 Connect-NaController : Connection to server01 using HTTPS failed - The request was aborted: Could not create SSL/TLS secure channel. The error may be resolved by generating a new certificate on the storage controller, with a longer key length. At line:1 char:1 + Connect-NaController -HTTPS server01 + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidResult: (msfcnf01:NaController) [Connect-NaController], NaConnectionSSLException + FullyQualifiedErrorId : HttpConnectionFailed,DataONTAP.PowerShell.SDK.ConnectNaController
OnCommand System manager to the same exact filers is working fine from the same server that is exhibiting the PowerShell failures above.