Reference level overrides is off.

(Posted on behalf of the user)

I'm trying to override the element symbology of an attached reference file using the level manager and it is giving me this message:

"reference level overrides is off. level change is valid only in current session. the change has not been written to file."

Where is this setting and how can i change it?  it's only happening in certain files.  Other files, I can change the symbology of reference files using the level manager override and it saves it.