Bug/Issue Steam Achievement for Beating "Journey of the Prairie King" isn't Unlocking

Hey y'all,

I'm not sure if this is an issue others have had or not, but I've been trying to 100% the game on Steam and am a decent proportion of the way there, however, the achievement for beating "Journey of the Prairie King" hasn't unlocked despite beating the game twice. After it didn't unlock the first time, I thought maybe my internet had bugged out, so I made sure that I had ethernet connection the second time and it still didn't unlock.

I'm not using any mods, and am getting really deterred from playing the game since my goal has been to 100% it but this bug isn't allowing me to.

Is this a known issue? Does anyone know how to fix it?

Any advice helps, thanks!