When I open the mirrored EDL in Avid DS, I get an error message & the first event fails to load correctly. What am I doing wrong

By default Avid DS autodetects CMX format EDLs by looking for an "FCM" line which says whether the EDL is drop frame or non-drop frame. EDL Mirror does not include this (optional) FCM line so you have to force DS to load the EDL as CMX format. The notes on how use EDL Mirror with Avid DS cover how to do this.