That looks like a .yml spacing error. Post the permissions.yml from from PermissionsEX on pastebin and I will try to fix it.
You can also reset it if you want, if you have not set much permissions yet, delete the permissions file and start your server so PEX can regenerate a default one.
Exactly as strawberry3x said above, it is most likely a spacing error. If you post the permissions we will be able to assist you. It could be as simple as a missing or added space.