My update stalled at 63% on the installation.     I waited 1/2 hour and nothing changed.    I disconnected and now nothing happens when I plug the USB connection into my iMac. The assistant program does not auto connect to the Spark.   Now what ?

Hi, Joe. I would recommend you reinstall the DJI Assistant 2 from our website. Please ensure that you download the latest IMac version. Here is a video for updating spark by assistant.