My Slicer version: 5.2.2 r31382. I could load NIfTI-1 file in Slicer, but I could not load my NIfTI-2 file in Slicer. Is Slicer does not support NIfTI-2 file format?
Please try with current Slicer version (right now the latest Slicer Stable Release is Slicer-5.4.0).
If it does not load the file then it means that ITK library (that Slicer uses for image reading/writing) cannot read this file format or its support is not enabled in Slicer. In this case, I would recommend to ask about status of NIFTI-2 support in ITK on the ITK forum.
I upgrade the latest version of Slicer 5.4.0, but I got the same problem. I will look at the ITK forum. Thanks for the link.