Mathematica 12.0 and BibTeX reference problem (Windows 10)

I have problems getting the Citation Management in Mathematica 12.0 to work. It does not work with either EndNote or BibTeX. To do a minimal example, I have the following BibTeX file (libra.bib) having only one reference:

@Misc{elliptic,
author = {Wolfram, Stephen},
title = {Solving the Quintic with {M}athematica},
howpublished = {http://library.wolfram.com/examples/quintic/},
year = 1999
}

When trying to Add Citation (using BibTex file) I get this error:

Any suggestions?