Hey,
Firstly, i’m quite certain my unity setup is correct, as Galaxy S4 works.
I’ve tried googling for afew links for answers but it doesnt work 
USB is connected, USB Debugging is enabled and installation from unknown resources is allowed.
Please help me
Although I haven’t encountered exactly same problems, but it was similar. Generally I do testing with a symphony mobile. One day I intend to test on a Samsung mobile. I did USB is connected, USB Debugging is enabled and other setting ticked. But unity still say no device connected! Haven’t looked it further. I guess you should remove/update the usb driver for mobiles.
does the SDK support your HTC phone?
I would open up your SDKmanager.exe and make sure.
a simple SDK update may solve this.
How do i remove/update the usb driver? i already have it installed but i cannot remove it
– fengwuqueOn windows 7, Control Panel\\System and Security\\System. Then on left, click "device manager". Find your device (probably under "human interface devices"). Then right click on it. Now do "update/uninstall/update" etc. I would plug the device first, then do remove the driver. While removing; I would disconnect the device; Then I would freshly install stuffs after; If I were you.
– kaiyum