Download and install the updated driver and if it's still showing "not connected", then it's time to take the laptop to the shop, or have the company fix it due to warranty.
Hope this helps.
Grif
Hello! I have a Dell Inspiron 7548, Windows 10. I've never had any problems with the touchscreen feature, until just recently. Out of nowhere, it just stopped working. I tracked the problem to my device manager, where the HID-compliant touchscreen driver was "not connected" (Code 45). After fiddling with that for quite some time, I took the advice of a friend and simply reset the computer (granted, this is after restarting the computer multiple times to see if that were the problem). Once reset, the touchscreen still isn't working, and now my touchscreen driver isn't even there anymore (and it's not in hidden devices).
I've run all updates, tried every troubleshooter, and done everything I could possibly scour the internet for and NOTHING helps. Please, I'm at my wit's end. I use this feature everyday and it is an integral part to my work. Please help!
Thanks!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic