There are two known reasons that this error can occur:
On Windows, HDFView was built with VS 2015, and it requires that the Visual C++ Redistributable Packages be installed on your machine. If you cannot access HDF5 files then you may not have these packages. You can obtain them from: https://www.microsoft.com/en-us/download/details.aspx?id=48145
This error can also occur if there are unicode characters in the path or name of the HDF5 file. If you remove the unicode characters from the file and/or path, it should correct the problem.