Make sure you use the original power adapter and USB cable because if not, that might be the reason why your phone isn’t charging at all. Remember, a battery as huge as the S7 Edge’s need a powerful charger and considering it’s capable of fast-charging, you need something that’s specifically designed for such feature.
Check both ends of the cable for corrosion, debris and/or lint. Anything that goes between the receptors in the phone and the pins in the cable may interfere with the normal charging process. Be also on the lookout for bent or crooked pins. If you can find one, try straightening it out.
Inspect the port on the power adapter. Try to see if there is corrosion of some kind or bent pins. You also need to check the USB or utility port on your phone for the same thing.
Assuming there is nothing that blocks or corrodes the pins, try turning off your phone and plug the charger in to see how the phone reacts. If it shows the usual charging symbol or lights up the LED indicator, then the charger is ok as well as the cable. However, if the phone doesn’t respond, then it might be an issue with the adapter or the cable and to rule out these possibilities, you need to use a different charger. If the phone charges fine with other chargers, then you need to buy a new charger kit, otherwise, continue troubleshooting.
If the phone won’t respond when plugged in, it might be a simple system crash issue.
Perform the forced reboot procedure by pressing and holding both the Volume Down and Power keys together for 7 to 10 seconds. The phone either reboots or the screen flickers for short time. You can then try charging your device and see if it responds this time.
Boot your phone in recovery mode if it still didn’t respond when you plugged it in. In Android System Recovery, all necessary hardware are powered up but the Android GUI isn’t loaded. So, if it’s not a hardware issue, your phone should be able to boot up in recovery mode: press and hold the Home, Volume Up and Power keys together.
If the phone won’t boot up in recovery, it’s time to have it replaced because it might be a hardware problem. However, if it started fine, then try wiping the cache partition. If that didn’t make any difference, then try doing the reset still through recovery mode. In case the phone remained off (and didn’t even flicker), there’s a chance the battery was all drained and since the device won’t charge, seek help from a technician.