Hello,
Can you please confirm which end is HDMI and which end is DisplayPort?
These converting cables have a direction. They will only work as source DisplayPort and monitor HDMI, not the other way. The cheaper cable work because the DisplayPort connectors can output HDMI signals (it is called dual mode DisplayPort or DP++).
I do not know of any consumer adapter you can purchase to convert HDMI signal to a DisplayPort monitor. If it exists, I believe it will still be cheaper for you to purchase a standalone USB->DisplayPort adapter:
https://www.displaylink.com/products...num=1&vid_dp=1
Regards,
Alban