Procurement Tile disappearing for users.

Summary:

Hi there, I am wondering if anyone could help. For the last 6 months or so users within our Education Network have been losing access to the Procurement tile intermittently, sometimes they would log in and it would be working fine and others the tile would be missing. This does happen with our Corporate Network also, however users just log out and back in again and the tile reappears. However with the education users, it is no longer intermittently, once they lose the tile, the tile is gone and does not reappear. This is causing great frustrations across our services