At the download site for the OpenNTF XPages Extension Library there is a small note for the last two releases 901v00_12.20150311-1316 and 901v00_13.20150611-0803:
“Please be aware of technote SWG21696682 as it affects the installation of the Extension Library if the UpdateSite.nsf method is used.”
What this note actually means is that if you are using an UpdateSite.nsf on a Domino 9.0.1 server with FP3 or FP4 to install the Extension Library you are in trouble.
With both Fix Packs a security change in java.classforName in the JVM prevents any Extension Library to be loaded. There is no error message on the console. The Extension Libraries are simply not available.
For FP4 the solution is simple: Install the JVM Patch SR16FP7 as described in the IBM technote “Interim Fixes & JVM patches for 9.0.1.x versions of IBM Notes, Domino, iNotes & Notes Browser Plug-in”.
After installing the JVM Patch SR16FP7 you will see a again the beloved message on the console: “...NSF Based plugins are being installed in the OSGi runtime...”