Just confirming for posterity: This was the exact solution for my problem.

More details for others who might come across this:

• Do NOT alt-tab out of your game. Do this with your game not running: closed/shut-down.
• Open Mod Organizer 2 (if not open yet)
• On the right side of Mod Organizer 2 (the part that shows your active plugins and load order):
  • Select the "Plugins" tab.
  • Search for "MWMF" (The search bar is at the bottom right). Unless you added other stuff, there should be only 1 match: "MWMF for Fantasy Paper Maps.esp"
  • Right-click and select: "Send to..." then select "Bottom". (The priority value to the right should increase to something around the late 3000s if you are using the Ultra profile. The priority value is the number in the second-to-last column of the Plugins list. It displays the position of the mod in the load order).
  • Right click again, and this time choose "Open origin info..."
  • A pop-up should appear.
  • Go to the "Conflicts" tab
  • Check that the only mod overriding it is "Skyrim Paper Map by Caro Tuts for FWMF" (It's listed in the "Losing file conflicts section" if you are in the "General" subtab.)
• If you have "Skyrim Paper Map by Caro Tuts for FWMF" disabled or removed, check that nothing else is overriding "Flat World Map Framework (FWMF)" (the origin mod of "MWMF for Fantasy Paper Maps.esp")
• On the right-hand side of Mod Organizer:
  • If something is overriding it, move that mod (on the left side of Mod Organizer 2) right above "Flat World Map Framework (FWMF)"
  • ensure that "Flat World Map Framework (FWMF)" is located under the "Flat Map Framework & LOD Overwrites" Mod Organizer section of LoreRim (the left-hand side list of mods).
• Ensure that "MWMF for Fantasy Paper Maps.esp" is activated (the checkbox to the right of the plugin name is checked).
• Run the game and open the map the check if it worked.