This link: http://askubuntu.com/questions/763735/ubuntu-16-04-blank-screen-at-bootup/871156#871156 was helpful to me. It fixed the problem.
This link: http:// askubuntu. com/questions/ 763735/ ubuntu- 16-04-blank- screen- at-bootup/ 871156# 871156 was helpful to me. It fixed the problem.