I haven't tried PS 5 with PSTK 4.3, but there should be full backward compatability with both.
What error is you NaConnect cmdlet returning with ?
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff, Sr.
Independent NetApp Consultant http://www.linkedin.com/in/eugenekashpureff
Senior NetApp Instructor, Fast Lane US http://www.fastlaneus.com/
(P.S. I appreciate 'kudos' on any helpful posts.)