The default for POSH is to use https and if failed it will drop to http. if you want to set it to use https or http directly, just use the -http or -https parameter when issuing the Connect-nccontroller.
PS > Connect-Nccontroller -Name cluster1 -http or -https
which network IP address are you using to connect via PS (cluster-mgmt lif or node mgmt-lif etc...)? and is it the same IP used to connect to sysmgr.
Also, can you share the output of the connect-nccontroller with -verbose paramter.
To get http to work while troubleshooting the reason behind https not working, check wether it is enabled on the cluster level:
cluster::> system services web show
External Web Services: true
HTTP Port: 80
HTTPS Port: 443
Protocol Status: online
Per Address Limit: 80
Wait Queue Capacity: 192
HTTP Enabled: false
HTTP is disabled by default, you can enable using the command below:
cluster::> system services web modify -http-enabled true
Hope this answer your question.