1.1.5 ssinvite command not working

[Pewx]

I am running a clean Tekkit 1.1.5 server with MCPC+. Have not added any plugins or changed any configs. and when an OP types the /ssinvite command it works fine. But when a non-op writes the command the following error appears:

"I'm sorry, but you do not have permission to perform this command. Please contact the server administrators if you believe that this is in error."

Does anyone have any idea how to solve this?

Thank you

[soulscapex]

Ive also been looking for the required perm needed for users