Please help, my MacBook Pro won't connect to my external monitor

Right before the update my external monitor was working fine. After I restarted my computer and applied the latest update my external monitor won't connect and my monitor on my MacBook will just continuously switch on and off. I've already tried restarting my MacBook while the external monitor is connected and I've tried factory restarting my monitor but I still get the same results. Any suggestions as to what else I can do?