I am trying to set this stage as my Sentinel's stage. (sentinel, stages/Operation genosha.def)

for some reason, this stage will not pin onto him. In fact, when I try to set this stage onto other characters, I have this same problem.
Am I doing something wrong? Please, any help for this minor inconvenience would be appreciated.

I'm a mugen noob so forgive me if there is an obvious error I've overlooked.