Due to a somewhat recent update with either Ircam Verb and/or Reaper, Ircam Verb and the Sessions version would receive input but not produce output upon reloading a project. Maybe this is only affecting older projects that had a previous version of Ircamverb (which I had recently updated). The fix I found is to enable the check for the "inform" setting (this is a global parameter)and/or also changing the channel count to something different and changing back to the previous count. Then reload the plugin/project to test. A better fix may be loading a new instance of Verb and using that instead though.