Hi
I have SCR44 white version for Z5 compact white and it worked fine. My collegue has a SCR44 black version and the screen has the same problem as yours.
Putting on the white cover to a black telephone (Z5C), the Z5C screen worked immediately. In your case Z5/ SCR42, I beleive it's a problem with the case itself. Return it back to the shop and try a white one and check to make sure your phone is not a problem to interface SCR covers.
Observing the quantum of problems popping up in this forum, every product from Z5 series and it's dedicated accessories have one or more problem with regards to manufacturing quality. Customers are very unhappy and on other hand many are jumping in joy seeing Sony has introduced defective products into the market.
I have to return my Z5C white back but I am uable to return SCR44 cover. Another lesson learnt which costed me NOK 299.
All the best.
