Screen Fault

Hello Ginkidijay,

Welcome to Apple Support Communities. I understand from your post that there is a single horizontal line that has appeared on your MacBook Pro screen and are seeking advice on how to fix it. I am happy to help you.

Let's try an SMC reset. 

How to reset the System Management Controller (SMC) on your Mac

You may also want to try an NVRAM reset. 

Reset NVRAM or PRAM on your Mac

If you're still experiencing the issue after performing the above tasks, then let's try Safe Mode. Safe mode (sometimes called safe boot) is a way to start up your Mac so that it performs certain checks, and prevents some software from automatically loading or opening. 

Use safe mode to isolate issues with your Mac

Let me know how it goes. 

Have a great day!

Yep, the 2011 MacBook Pros and iMacs had the infamous AMD GPU failure. Apple had a repair program for this but has now ended. If you can get your money back, I would recommend it.

Please upload a picture. It's impossible to tell you what's wrong with your screen without looking at it.

Definitely looks like a GPU failure. Is this a 2011 MacBook Pro?