Mini Grbl k40 set up assistance

So I got my mini grbl fo k40 mini and installed it. I have a green light in the board and a flashing red light too, plugged into a Mac and into hp windows 10 and it doesn’t recognise the machine - at all. Open grbl on the pc and no ports to choose. Any suggestions?

Flashing red on a smoothie indicates an error. Do you have an SD card inserted?

The Mac will connect fine - it’s all I use for Smoothies.

Check Apple > about this Mac > System Report > USB. If it can see the device, it will be there. Connect first, then check - Command+R to refresh the display.

Run through this: https://awesome.tech/mini-gerbil-debugging/

I changed the cable and it worked - I must have been using a charge only cable. It seems to be plug and play - will test properly over the weekend