P2419HC, USB Type-C, no USB data transfer

The issue and all of the troubleshooting you have performed:

P2419HC is connected using USB Type-C to USB Type-C cable provided to a laptop with Thunderbolt 3 port. This was working fine until one day, the mouse connected to the monitor's side USB port is not detected. The mouse is detected when connected directly to the laptop. I tried connecting my phone to the monitor's USB port, charging works but unable to transfer data (not detected to select data transfer on phone). I tried connecting flash drive, it is not detected.
All this while my P2419HC is still displaying well and working, just that the side USB port and back USB port not detected. Device Manager shows that "Unknown USB Device (Device Descriptor Request Failed)" and USB is detected as Dell P2419HC (USB Type-C).

Troubleshooting done:
- Update drivers.
- Unable to update firmware as P2419HC not detected.
- Dell Display Manager Application (just because).
- Reset to factory.
- Self-test.
- Build-in diagnostics (all colours are fine).

To what specific PC model is the monitor connected?
- Lenovo Thinkpad T480

What operating system is running on the PC?
- Windows 10

What specific video card GPU is installed in the PC?
- Intel UHD Graphics 620

List all of the video card GPU video out ports?
- Integrated graphics only

Then detail how the video card GPU is connected to the monitor like this =
Laptop Thunderbolt 3 port -> P2419HC USB-C