If your Dynamo 800X is not powering on via the 12V trigger connection, there are 2 things to check:
1. Please verify the "Power Mode" switch on the back panel is set to the middle setting labeled "Trigger."
2. Dynamo 800X needs to use a Stereo 3.5mm connector for the 12V trigger input. The trigger will need to drive 12V on the "left channel" of the connector.