000545 : Input label engine must match output label engine.

Description

The input annotation feature classes do not use the same label engine as the selected output annotation feature class. The Standard Labeling Engine and the Maplex Labeling Engine make use of different labeling placement parameters, and these parameters cannot be combined into one annotation feature class. To determine which labeling engine the feature-linked annotation feature class was created with, right-click the annotation feature class in ArcCatalog, click Properties, then click the Annotation tab. In the Feature Class section under Label Engine, it will list the label engine used when creating the annotation feature class.

Solution

Select a different annotation feature class to append into or create a new annotation feature class to append into using the tool.