I had a ESbeta1 java client connecting fine to ES. I upgraded both server and client to 2.0, and installed marvel too to check it out.
Suddenly the java client could not connect any longer. I tried to tweak discovery (unicast, multicast etc) to no avail. I enabled trace logs and saw some errors like this (sorry I deleted old log files so I dont have the whole stack trace):
No custom metadata prototype registered for type [licenses]
Eventually removed both plugins I had (marvel-agent and licenses), and this fixed the issue. I searched but found nothing similar reported. Did anyone see something like this? Note that I was still in the month of evaluation of marvel.