My Galaxy S7 (Exynos) stuck at Download Mode and not charging.

[Subhojit Karmakar]

I have been using my Galaxy S7 with a custom ROM since a while. After flashing a different ROM which I've used before it triggered FRP lock which is also fine. Then when I tried to flash an offical from downloaded from updato.com it got failed and showing a blue screen containing "An error has occurred while updating the device software.....". So I kept my device as it is so that I can download another Official Firmware from a different source/built. Next day the battery got fully discharged and I then put the phone on the charger for an hour or two to flash the latest downloaded firmware. But after disconnecting the charger it stays on for a few seconds and then it goes black. So there's not enough juice left to flash the new firmware via Odin. Whenever I tried to flash it via Odin it starts flashing the recovery then system but the phone shuts down after a few seconds before it even finishes. I have tried charging the device for several hours but no luck. It just stuck at the above-mentioned screen while charging but after disconnecting the cable it turns off.