Map Builder doesn't work!

When I use the Map Builder feature by clicking “Check out the Map Builder to easily place your area on the map!” option on top of the location page(s) in the map, it doesn’t load, and instead is giving me the following error:

There was an error loading this world.
If this error continues, please submit a bug report with a screenshot and we'll look into it!

I’ve tried it in multiple different campaigns and I guess it doesn’t work because it cannot reach the world and keeps opening the following link with the”/undefined/:

https://play.fables.gg/worlds/undefined/map

How may I fix this?