Hi,
The problem should be purely in UWL/Portal side. The "not reserved by agent" should not have anything to do with the problem - it is a normal "status" in SWI5.
You could check if the task is maintained in SWFVISU transaction. If not, add it there.
If the task is in SWFVISU, then basically the tasks should appear in UWL. You could re-register the backend system. Do this in portal in System admin -> System configuration -> UWL -> Find your backend system alias in the list, and click the re-activate (or activate) or whatever. On the above portal page you should be able to find "Cache administration" link. Click it, and refresh all the possible caches & expired items etc.
Of course it is possible that the whole UWL and its connection to the backend system is not correctly setup, but in this case you should not see any tasks from the backend system
Regards,
Karri