Are you using a non-Education version at work?... because non-EDU versions will not show the Circuit Restriction command, it is built-in the EDU versions. If this was the case then you need to unlock it first on a EDU version, save it, and then re-open it in your normal Pro version.
In case you are using a EDU version also, then you need the unlock code from the last person that lock it. The password is embedded on the file itself, is not a separate file.