If create disk is working without any issue, then I don't suspect any issues with host-side disk discovery and filesystem formatting. Ideally, disk connect operation should have worked fine as create operation is succeeding on the same setup.
Is this disk that you are trying to connect previously created via SC and then disconnected? or Are you trying to connect a lun that is created from the ONTAP side ( not from SC) which is not mapped to the host using any igroup and you are trying to do that via SC?
Please try the workflow which is Create disk from SC-> Disconnect disk from SC--> Connect disk from SC