Thanks for reaching out to us, I am sorry this is not working as expected and I am happy to help!
Please let me know the manufacturer name and model number of the display connected to the adapter.
How long is the HDMI cable being used, is it possible to use a second cable of six foot ( aprox. 2m ) or less to connect to the display to see if this works? Longer HDMI cables require more power to send a strong signal to the display, the adapter has to use some of the DispalyPort’s power to convert the signal to HDMI leaving less to drive a long cable.
Additionally, just to clarify, is the DisplayPort end of the adapter connected to the computer’s DisplayPort output? This is a one-way adapter from a DisplayPort output on a computer to a HDMI display (monitor, television, or projector), it will not work from a HDMI output on the computer to convert to a DisplayPort monitor.
Thank you for these additional details, they will help to determine our next steps.