Picture looks good so far ... here is what I will suggest off-hand ..Copy the material of one and then change it to a solid form ... render real quick just to se where the shadow would be. Paste the material back ... It might be that that glass all is too transparant to be have deep shadows ... Also try making the table white so they would be very visible. Also .. when all is said and done the best thing I have found is to compare the properties between one that worked and one that doesn't. Whethere it is transparanies or shadows that aren't working. Good luck