Thorsten,
net-port-ifgrp-get is ONTAP API and its present on 8.3.1 CMode. Are you sure about your cluster being 8.3.1 Cmode?
Can you try the below and post the output.
1. Login to your WFA windows machine and to to WFA/bin folder
2. Double-click to launch ps.cmd file . It will launch the powershell with the WFA and ONTAP modules loaded
3. Run the below cmdlets. You should get the output as given below in green.
PS C:\Program Files\NetApp\WFA\bin> Connect-NcController -Name <cluster-ip> -Credential <user-name>
Name Address Vserver Version
---- ------- ------- -------
10.226.162.45 10.226.162.45 NetApp Release 8...
PS C:\Program Files\NetApp\WFA\bin> Get-NcNetPortIfgrp
IfgrpName Distribution Mode Ports Nod
Function e
--------- ------------ ---- ----- ---
a0a port singlemode {e1d} f32
PS C:\Program Files\NetApp\WFA\bin> Get-natoolkitversion
Major Minor Build Revision
----- ----- ----- --------
3 3 0 62
PS C:\Program Files\NetApp\WFA\bin> Get-NcSystemVersion
NcController Value
------------ -----
10.226.162.45 NetApp Release 8.3.1X5: Sun Mar 15 0...
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