First, make sure it’s not user error. If there’s no picture, verify the projector is on the correct input channel and that the lamp is powered on. If there’s no sound, make sure neither your projector nor your phone is on mute and that the volume is at your usual listening level. If all of those details are in place, this likely means there’s an issue with the equipment that you’re using. It could be that your adapter isn’t quite compatible with your phone. Double-check the adapter’s stats against your phone’s and your projector’s and buy a different adapter if it doesn’t match. The cable can play a role in this too, especially if you’re repurposing an older cable you had laying around your house. Just because the connections fit doesn’t mean it’s the right cable for your signal type. Buy a new cable that’s certified to be used for your devices and connection method and this should solve the problem.