I can't to turn on the grid screen in my viewfinder.

[JGRICE1234]

I went to C. FnIV, highlighted #1 but there is no grid in the viewfinder. What's up?

[Jason]

Hello JGRICE1234.  The community is eager to assist!  To ensure the most accurate information is provided, we’ll need to know the model of the camera you are using.  We look forward to hearing back from you!

[p4pictures]

If you are changing a C.Fn then you have a camera that can take interchangeable focusing screens like an EOS 60D, EOS 5D Mark II, EOS 50D, EOS 40D, EOS 5D. On those cameras the change of the focussing screen is required to see the grid pattern in the viewfinder. However since the focussing screen is a bit different in brightness the camera needs to be told which screen is in use so it can adjust the cameras metering correctly.

On the EOS 7D for example that has an overlay it is possible to switch on or off the grid in the viewfinder. However you cannot change the focussing screen on this camera.

Brian / p4pictures

[7D5D]

Not knowing which body you are referring to, toggling the grid display on for Live View shooting is in the 4th shooting menu for the 7D and 5D mk III.  Sounds like the C.Fn is an enhancement for your body when the grid has already been enabled in the shooting menu first.

Check your shooting menu and see if it is even enabled (or if there even is a setting for your body).