The parcel fabric in the map has a feature class with a read-only CreatedByRecord or RetiredByRecord field.
Do the following:
In the Contents pane, right-click the parcel fabric feature class, point to Data Design and click Fields. Uncheck the Read Only property for the CreatedByRecord and RetiredByRecord fields. You may have to do this for multiple parcel fabric feature classes.
The CreatedByRecord and RetiredByRecord fields are system-managed fields. These fields are automatically populated when parcel features are created or retired by an active record in the map. These fields cannot be read-only. For more information, see Create parcel fabric records and Analyze your GIS resource.