Are all other notifications from other apps working normally? Do you have any power-saving modes or Restrict Background Data turned on?
Not sure since this phone is new to me by a few days.Did this start after a recent update to the app? Might be a glitch with the update. You could wait until the next update, although I don't know how often they update it. Send some feedback to them in the meantime.
Not sure since this phone is new to me by a few days.
did you transfer all of your app settings to the phone when you got it or did you sign in to everything manually? I had a similar issue with my first V20 and I had to sign out of everything and then sign back in to get notifications to work.
if that doesn't work, try settings -> device settings -> notifications -> apps -> facebook and make sure you don't have the app blocked or silently checked. also check the option to make facebook a priority app and see if that works.