Powered external monitor suddenly using too much power, USB disabled message

Hi. I purchased a new MacBook Pro (USB-C drives and track-pad) only 6 months ago. I've purchased an LG powered external monitor to run with it. I purchased a seperate USB-C to HDMI cable to connect it.

They have both been working absolutely fine together for the past 2 weeks and tonight suddenly, I get the error message: "USB Accessories Disables - Unplug the accessory using too much power to re-enable USB devices". I don't understand this as the LG monitor has it's own power supply plugged into the wall. And it was all working fine. I had the Mac power cord plugged in and an external MIDI keyboard and microphone. All working fine until now. All these other devices still work in USB-C without the monitor plugged in. I'm only getting the message when I plug the monitor in.

HELP. Why is it all of a sudden doing this? I just purchased this monitor and cable especially!

Any help appreciated.