Migration of Projects

Hi All.

I am migrating a project collection within a organisation.  When i moved the various Work Item Types, some do not recognise the new Area Path or Iteration Path, despite me either changing in excel when i tried via CSV, or in the box when i tried within ADO and therefore revert to what they were.  Ive tired to go in manually to each WIT and change, but the Area Path/ Iteration Path cant see the new project so i cant change them - whereas some items i moved are absolutely fine and i can see the new paths.  It looks like the Features are on the new path, but Backlog items/ Tasks arent.  What am i doing wrong?