The P2418HT was never provided with a Windows 11 specific INF/ICM/CAT driver or Windows 11 support.

The only reason Windows 11 appears is because the DDM 1.55.0.2090 supports Windows 7/8.1/10/11.

The P2418HT Touch support comes from the supported Windows 10 operating system. Online P2418HT User's Guide page 11 =

From the online P2418HT User's Guide, for touch to work in the supported Windows 10, you connect the provided USB 3.0 upstream cable from P2418HT #6 USB-B port to the PC USB-A port. Sounds liek Windows 11 is not providing a compatible touch driver.

* In Windows 11 Control Panel --> Hardware and Sound, look for Tablet PC Settings
* Click, "Calibrate the screen for pen or touch input"
* Right of Display: make sure it shows P2418HT
* Click, "Calibrate" and follow the prompts

I have a multi-monitor setup which included a Dell P2418HT on a Windows 10 PC. No issues with touch working in the old system. Switched to a new Windows 11 desktop and the touch screen would not work. Found a reditt thread that got me to this solution =

* Go to Control Panel---> Hardware and Sound
* Select Tablet PC settings. This creates a popup which asks you to configure your pen and touchscreen display
* Select setup and then follow the on screen instructions by pushing enter until the question comes up on the Dell P2418HT and then touch that screen
* Accept and close and it worked

Hopefully this helps you too!