Frank Black

Hi I have done a search on this topic but couldnt see a solution so apols if its something i missed. I have paid for the liscense to setup on my shield. Have sideloaded Retro64 and Launchbox is ready to go. Yes i am having the same issue of a blank screen. I have downloaded all the Mame Cores in Retroarch and set the core to Mame in Launchbox ( the one everyone recomends for Retro64) but nothing. Any answers or a link to an answer? thanks in advance