A DESCRIPTION OF THE PROBLEM :
Java+JavaFX implement CookieHandler twice. The default implementation implements an obsolete standard and many websites don't work with it. Thus the JavaFX team implemented their own, which implements a more modern and compatible version of the spec and which is installed automatically when WebKit is used.

This situation is confusing. Java should only need one cookie jar implementation. The code from JavaFX could be moved into the JDK so all apps benefit from better cookie handling.