First of all I advise that you use updated Google Chrome browser and Windows 10 for this to have the best chance of working
If you have visited the site before then you could try a hard refresh (ctrl+F5) or (ctrl + click refresh button). This will force getting the newest version of the website
"No compatible devices found"
You need to install a driver for the cable you are using.
Two are listed below depending which cable you have. It wouldn't hurt to install both, or ask if you are unsure.
Cable is listed but fails to connect to the car
Make sure you have one of the below drivers installed first.
If you are having issue when using the 3-pin connector in the engine bay then double check the state of the pins on the car side. Contact cleaner would be a good idea for corroded pins
Also check you are not plugged into a green connector which is for the alarm/immobiliser.
Prolific technology cables (3-pin cables I sell)
There is a driver package here for the Prolific technology cables, for Windows 10:
Download this, open it and then run install.bat to install it, it will try to remove any old drivers and install a working one only.