My screen won’t turn on

I'm sorry to hear about the issue with your MacBook Pro screen. It can be frustrating when the screen doesn't turn on despite the charging indicator showing that the laptop is receiving power. Let's try a few more troubleshooting steps:

1. Check the display brightness: Press the F1 key (or the Brightness Down key) multiple times to increase the screen brightness. Sometimes the brightness might be set too low, making it appear as if the screen is not turning on.
2. Connect an external display: Use an HDMI or Thunderbolt cable to connect your MacBook Pro to an external display or TV. This will help determine if the issue lies with the MacBook Pro's built-in screen or with the graphics card. If the external display works fine, it suggests a problem with the MacBook Pro's screen or display connector.
3. Reset the NVRAM and SMC: Resetting the NVRAM (Non-Volatile Random-Access Memory) and SMC (System Management Controller) can help resolve certain hardware-related issues. To reset the NVRAM, shut down your MacBook Pro and then press and hold the Command + Option + P + R keys while powering it back on. Hold the keys until you hear the startup sound for the second time. To reset the SMC, shut down your MacBook Pro, disconnect the power adapter, and then press and hold the Shift + Control + Option keys along with the Power button for 10 seconds.
4. Perform a hardware diagnostic test: Restart your MacBook Pro and immediately press and hold the D key. This will initiate the Apple Hardware Test or Apple Diagnostics utility, depending on your macOS version. Follow the on-screen instructions to run a diagnostic test on your hardware and check if any issues are detected.
5. Boot in safe mode: When your MacBook Pro boots in Safe Mode, it performs a basic check of your startup disk and disables unnecessary extensions and login items. This can help identify and resolve issues related to software conflicts or incompatible drivers. it might be a bit tricky, here's how to boot in safemode when macbook screen not to turn on.
6. Consider professional assistance: If none of the above steps resolve the issue, it's advisable to take your MacBook Pro to an authorized Apple service center or an experienced technician. They can diagnose the problem more accurately and provide the necessary repairs or solutions.

Remember to back up your important data before taking any further steps or handing your laptop over for repairs.

What is the color of the MagSafe connectors LED? Amber or Green as well as is it bright or dim.

I would give this a try: Carefully disconnect the battery following first Steps in this guide MacBook Pro 15" Unibody Mid 2012 배터리 교체 then press and hold the power button for a good 15secs to fully discharge the logic board. Reconnect the battery and charger then try restarting the system. Did that work?