We are having the same issue, in clearspace 2.5.4 it seems like a clearspace bug,
thing is if we first defined action,but not modify anything in ftl and buid the plugin everything is fine and after restart then if we modify the ftl and instead of rebuildingand restarting server we just flush the theme ftl files with ant task, it also works fine, and our action gets called and all is good,
but as soon as we stop the server and rebuild the whole thing then clearspace gets confused and all plugin actions are getting lost as if plugin's struts.xml file have never even been read,
and yes we did checked admin plugins to make sure plugis are listed their, even our plugin lifecycle init method gets called.
P.S: we are preparing a detail report on it ad will write a question in the forum shortly.