Grid missing on piano roll view?

  Hi,
When in the piano roll view, I cannot get the grid to show, so I can get a sense of where the notes are in relation to beats.
I have tried the "view > Grid resolution" options in the piano roll view, but no luck.
What am I doing wrong?
Many thanks,

Yes, I have.
I've fixed it though, I don't know why, but they weren't showing in the docked piano roll, but ok on the screenset one now.
all good.
Thanks FBB