Replaced screen and now camera and backlit keyboard not working

What's good Mac2019RQ? Replacing the screen on a MacBook Pro, especially a newer model, can be tricky and it's common to run into issues like these. Here are a couple of things to try:

• Double check the connections: There are a number of delicate ribbon cables that connect the screen to the logic board. It's possible that one of these cables became dislodged when you replaced the screen. You'll need to carefully open your MacBook Pro again and reseat all the connections. There are many guides available online that can help you with this process, you can find one by searching for "16 inch 2019 Macbook Pro screen replacement".
• Reset the SMC and NVRAM: The SMC (System Management Controller) and NVRAM (Non-Volatile RAM) are responsible for a variety of low-level functions on your MacBook Pro. Resetting them can sometimes resolve issues like this. You can find instructions on how to do this by searching for "Reset SMC and NVRAM Macbook Pro".

If neither of these steps work, it's possible that the replacement screen itself is defective or that you damaged something else during the repair process. If you're not comfortable troubleshooting the issue further, you can take your MacBook Pro to a Apple Authorized Service Provider for further diagnosis and repair.