Post your question on the Multisim Connectivity Toolkit thread (http://forums.ni.com/t5/NI-Labs/LabVIEW-Multisim-Connectivity-Toolkit-Beta-Discussion/m-p/773788). That product is still in Beta so not many people on the LabVIEW board has experience with it. The MCT Beta thread is monitored by the R&D engineers working on the product so you should get a faster turn around.
Please provide more details. What LabVIEW and Multisim version are you using? What error message did you get. Would you be able to post you VI?