It seems that RStudio detects that I'm using Firefox and sets the keyboard shortcut for Show Command Palette to Ctrl+Alt+Shift+P but that seems to override the shortcut for Run All Chunks Above.
I noticed that this Firefox-specific shortcut is mentioned in https://support.rstudio.com/hc/en-us/articles/200711853-Keyboard-Shortcuts-in-the-RStudio-IDE
It seems that Firefox has a built-in Ctrl+Alt+P shortcut to open a Private Window. The original shortcut for Run All Chunks Above was Ctrl+Alt+P so that seems to explain the override.
I imagine other people have had this problem, but I don't see it mentioned anywhere. I realize I could probably set a customized shortcut, but I'd really prefer if the same shortcut would work on all platforms with all browsers.
Thanks for any help.