If you have reset your landing page and have entered in the Facebook Image URL, but you are still not seeing the correct image on Facebook, please follow the steps below.
Go to: https://developers.facebook.com/tools/debug/og/object/
If you are still seeing the old image click on the Fetch New Scrape Information button.
NOTE: You will need to continue to press the "Fetch New" button multiple times until you see the correct image. There is no correct amount of times to press the button, sometimes you will only need to press it once, others up to ten times.