A Map Problem or Automated Problem Report comes from the Waze system when it detects something that is happening in the real world as tracked by the Waze client apps that does not match the logic in the map data. There are three options the editor can use to respond to these Map Problems: Solved, Not Identified, or leave it as Open. Just because you do not know the solution doesn't mean that another editor won't figure it out, so do not use Not Identified.
See the Global Wiki page on this subject.