Possibility: You had previously done the same search and had either archived the results or left them in DA’s cache. Your search set was configured to filter (not display) previously found results that are in the archive and/or the cache. And no new material had been added to the searched Web resources for the plugin(s) set. The result would be no results for the search displayed under the Pages or Digest tabs of the search window.
Could that be the case? Try with a different search string, e.g., DEVONtechnologies or EasyFind that doesn’t have results stored in the Archive or in cache. Also (assuming that you had not saved the search results for “devonagent” in the Archive), select File > Empty Cache and repeat the search for “devonagent”.
I doubt that it’s a .plist problem, but there’s no harm in deleting it and relaunching DEVONagent 2.0 beta 8. (And you can always reverse the process should you decide to revert to DA 1.x.)
To select a plugin for a search, just open a new search window and click on the small “Find” popup menu to the left of the search field. Then navigate to the submenu “Suche > Deutschland” and select “German Internet”.