Flex can't get to it's home screen

Flex stays as a black screen. It will go to netflix using voice command on remote but asks me to sign in each time. If I use voice to try to open youtube,  I get an error saying Flex is having trouble with the app and then goes black. Voice on remote then will no loger work. I have power cycled Flex box. I changed hdmi cable. This all began yesterday. Before that there was no problem.