Hi Sarah,

The block consists of objects located on layer 0, this is a common practice:

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2015/ENU/3PP-A...

So when you lock layer 0 - you cannot edit block attributes as they are on the locked layer inside block. AutoCAD gives you an alert in the Command window: "The object is on a locked layer."

So you need to avoid locking layer 0 because it's kind of a special layer in AutoCAD.