eagle library--updated footprint wont show in board
Eagle stores the symbol, footprint, and schematic information inside the project file itself. This means that once you insert a part, the part information is copied out of the library and placed in the .sch file. The link to the library is lost. 

In order to update the part in the schematic/board, you need to right click on the part and select "Replace":



Then select the part again from the updated library. As long as the connections are the same, the new part will be replaced in the schematic/board with the updated part. If there are pin conflicts, it will notify you.