If there is gumming of the pawl pivot lube, and if the shifter sometimes works but not always, then the correct diagnostic is to push the shift lever very slowly to see if it works reliably that way. Alternatively, test the shifter after warming it up slowly using a hair drier.

If so, it's good news, and vonfilm's recommendation should rectify the seasonal problem.
I say "seasonal" because this is the time of year that everyone's shifters act up for the same reason.

I settled on the very thin-bodied and foaming Liquid Wrench Lubricating Oil as my go-to for such re-lubrications of the shifter's pawl mechanisms, but any similar oil product should work as well if directed into the right places.