DDJ FLX4 blinking MIDI light / no data handshake

Hi,

I have 2 Dell laptops both running Rekordbox and Mixxx. Neither seem to be shaking hands with the controller. I have read lots of threads / seen videos and tried:

changing the audio device

trying ASIO4ALL

checking the 2 rear usb c ports are plugged in properly

removing usb c power to the controller

upgrading to an expensive high speed data and power usb c cable to make things go fast

using the usb c port on my laptop

using the usb ss port on my laptops which have a usb a port

downgrading to a standard usb 2 port in case the other options are too fast

all above options with and without the controller power cable

changing power settings from 5 mins to never

everything else set to never / disable power saving

in device settings under usb uncheck allow turn off usb device to save power

in rekordbox and mixxx try to set the audio settings to DDJ FLX4 but its not there

rolled back 3 recent windows updates. One of the laptops had not been used for 3 years and I had a PC shop give it a service, so its shiny now.

I know its great that Windows picks up these devices and no drivers or firmware is needed, but it would be an advantage to have something to help get on track. I visited the driver and firmware page - there is nothing to download so I can't give the controller a kick.

I have just been offered a regular slot in a bar and my trial shift is this Friday! It would be great to have it all working so I don't have to tell them in advance that my laptop and controller aren't talking, and my spare laptop is sulking

Thanks for your help