Lervia KH4000?

I have a lervia kh4000 everything was working great until I changed the lower thread colour on the bobbin, prior to this I broke a needle so had to undo the bobbin casing by undoing the two black plates either side of the outer circle which hold the actual casing inside... now even after putting it together I cannot get the top thread to automatically thread the lower thread even by doing it manually it doesnt stitch the lower thread .., have googled for images where the actual casing is supposed to sit in the machine but no luck :(