After successfully repair your iPhone 6s screen, you try to turn on your phone and boom you just find out that your iPhone touch screen digitizer does not work, here is some troubleshooting you might need to do and make it work again.
Your phone might have not been assembled correctly
In case of assembly issues, just remove the brackets connecting the flex cables, remove the battery and press the power button for 10 seconds. This helps in draining the battery reserves. After a few minutes, reconnect the cables and return the brackets to their position. reconnect your battery, screen and turn on your phone.
Most times, when you replace the screen without removing the battery, you might see smoke coming from the connectors. This means your backlight has been burnt up. the only option is to buy a new iPhone 6s screen replacement
When you notice this problem- your LCD won’t come up after you have replaced the screen. It may be because of poor power distribution. All you have to do is a reboot, Switch off your phone, remove the battery and wait for about a minute before you turn it on.
Flex cable issue
The screen is connected to the motherboard through the flex cable which is covered by the brackets to protect the flex cable. If the flex cable is damaged, you will need a new iPhone 6s screen replacement
You may have gotten a defective screen, you may need to replace it.
if you tried all the above and your iPhone 6s touch screen still doesn’t work, you might need to upgrade or buy another used one.