After using 'out-of-the-box' activation couple of times, I get the Ok message but Inbox stays empty.

Message I get is:

"The workflow was successfully started. The item was sent to appropriate inbox."

There is no errors in the log files except multiple warnings like this one:

WARN info.magnolia.beancoder.MgnlNode 25.05.2007 12:04:00 – setProperty(openwfe.org.jcr.beancoder.JcrBeanCoder__instance_class, Null with type PropertyType.NAME, will switch to PropertyType.STRING ...

Since it mentions OpenWFE I think this could be the problem...