What agency has the POA paperwork?

Read the POA. Your daughter should have the signed original. Many places will not accept a photocopy. If you cannot find the original, get a new attorney and draw up a new POA for the state you are in now.

Are you asking if you can get a copy of someone's Power of Attorney, or your own, and if so, how and where?

Some local governments will keep copies of POA's on file, others do not. It depends on what is commonly done in your area. If you know who was the Attorney who drew up the POA, then that office would have their own copy, but you can only get a copy if you were named in the legal document.

Copy of my own POA..from Fresno, California my daughter is my POA. Does a POA expire? The attorney has passed away and the office closed.