If I click the New Bibtex Entry button, paste this DOI:

http://dx.doi.org/10.1016/j.engappai.2016.01.001

into the ID field, and then click the Generate button, then Jabref successfully downloads the article's BibTeX entry.

But if I instead paste the article's title into the ID field, change the ID Type to Title, and then click Generate, I get the error shown in this screenshot:

I'm using the title string:

Traffic flow optimization: A reinforcement learning approach

This is with:

JabRef 3.8.1 windows 7 6.1 amd64  Java 1.8.0_111