For some reason I can no longer advance the selected image from the film strip by pressing the left or right arrows. I thought I had a defective keyboard (after a small coffee spill) so I replaced the keyboard but to no avail. Hopefully someone can help me resolve. The up and down arrows do work in the G view mode but no lateral movement with the L R arrows.
Are the left and right arrows failing in the Library module or Develop module? It is possible for arrow keys to not affect the filmstrip/grid if keyboard focus is on a field or control, because then the arrow keys adjust the control. Whenever that happens, you can override that by adding the Command key in macOS (Ctrl key in Windows). So try pressing Command-left arrow or Command-right arrow.
If absolutely nothing in the current module has keyboard focus, the left arrow or right arrow alone should be able to move through the filmstrip. One way to try and escape all focus modes is to press the Esc key until the left arrow and right arrow work in the filmstrip.
Thanks! You won't believe what the answer was....I'm an idiot! When the keyboard didn't work but the laptop keyboard did, I assumed it was damage to the keyboard from a coffee spill. So I received a replacement, used keyboard for $20. Unfortunately I mixed up the new keyboard with the old one and reconnected the old keyboard! Eventually my son recognized the mistake and the replacement keyboard does, indeed, work fine. Thanks again and cheers!