Hi Thomas, thank you for replying and I had already checked to make certain the service was Sync enabled. The service is hosted on ArcGIS Online.
But, I found the issue today. One of the layers was an old data set that was not cleaned up and consisted of several multi-part polygons. After cleaning up this layer and uploading a new service, I am able to download maps to Collector from ArcGIS Online.
Again, thank you for the help.
Doug