U2419HC, MacBook Pro, no USB Type-C signal error

Hi

I have three U2419HC monitors in three different work locations. All have been working perfectly until last week when one of them wouldn't connect and started displaying this message:

No USB Type-C signal from your device

Because it won't connect, I only have the limited OSD menu showing inputs. I've selected Auto and USB-C but no change. I've done the 8 second reset but no change. I've tried three different cables, no change. I have it sitting on my desk next to another U2419HC which is working fine. I've plugged the working U2419HC into the same MacBook Pro USB-C port I was using with the faulty U2419HC. This suggests that it's an issue with the monitor and not the MacBook Pro.

When I plug the faulty monitor in to the MacBook Pro USB-C port, I get a charging chime from the MacBook Pro and a small window on the U2419HC saying, "Scanning for signal", followed by a second window saying "No USB Type-C signal from your device.".

So the monitor knows it's being plugged in and it's supplying power to the MacBook Pro, but it just doesn't want to read the USB Type-C monitor data being sent by the MacBook Pro (my second U2419HC works fine on the same port with the same cable).

I've also tried it with a second Apple Laptop (2018 MB Air) and have the same problem.

Does anyone have any suggestions? I noticed another question about this problem but there weren't any replies. Here's hoping.

FYI, I'm running a MacBook Pro (15" 2017 2.9GHz i7) on High Sierra. The U2419HC is 13 months old so frustratingly a month out of warranty!

Regards