Hello Tracy,
My guess is that you can't enter the lock code. This may be related to system freezes (due to some incompatible application) or damage to the screen itself. You do not write what condition the screen is right now and what happened to the phone before (e.g. whether it fell or got wet). This moment, You can use the safe boot option: press the volume up button, volume down button, then press and hold the power button. Hold it for as long (about 10 seconds) until the screen turns off - then release the power button. The phone will reboot and the touch function will be restored. Otherwise, you'll need to replace the screen to pass the lock screen.
Sometimes it happens that replacement Chinese screens stop working, mainly due to low-quality components. Tell some more, I'll try to help.