using $10 vouchers

i am new here. those who are new please take note. After buying shares and waiting for 6 working day, my voucher wasn't credited. so I checked with helpdesk..then I was told that what I have bought is a reit and not entitled to the 10 dollar voucher....
it says that the vouchers are only for purchase of common stock. so I ask them for examples of common stock.... no examples given. hope moo moo can make it clearer in future.