Unnapproved Caller SecurityAgent may only be invoked by Apple Software

Hello RichardBMoore,

Welcome to Apple Support Communities!

If we understand your post correctly, you're experiencing a "SecurityAgent may only be invoked by Apple software" error, and we'd like to see if we can assist. 

We recommend starting in safe mode. Sometimes just starting in this mode and then restarting can resolve issues like this: How to use safe mode on your Mac

You can also create another user on your Mac and test to see if you experience the same issue. 

Set up users, guests, and groups on Mac

Does this message appear when using any certain applications on your Mac?

Let us know if you have any questions.

Thank you for using Apple Support Communities.

Take care!