Writeback not working

[BKhanna]

I am trying to test the writeback functionality of Analysis Services. I enabled a cube for writeback, created a role that has read/write access to all cells in the cube (Cell security, advanced, unrestricted), then used the Excel add-in to retrieve data at the lowest levels for every dimension. When I select 'begin what-if analysis' on the addin menu, the cells do not turn green as they are supposed to so that I can update the data. It allows me to type in data and commit, but the writeback table is still blank. Does anyone know what could be wrong?

Thanks.