Passable Mountains Glitch Help

[Creepers99]

The mountain tiles in my game are passable by land units, does anyone know why this is or what might have triggered it? Is there a way I can change it?

 

[Browd]

Are you playing as Carthage, by any chance?

 

[Creepers99]

Are you playing as Carthage, by any chance?

Nope, Japan.