Church laptop is linked to a monitor to display things on the big screen. I can get sound but no picture, can somebody please

[busymomof2]

I am doing VBS this week at church and we have a laptop hooked up so that we can show videos on the big screen for everyone to see. I am using the VBS videos from youtube and I can get sound but no picture. Any suggestions would be appreciated. I really need information today as soon as possible. We will be meeting tonight at 6 and I really would like to get it working for the kids!!

 

[AppleGwava]

have you tried pressing either f8 or fn f8 as that changes the output,you will want to select either duplicate or projector only.Also could you add more information about the setup,what cables are you using etc