I'm a developer, and I'm always trying to learn and study different courses and searching for specific topics I come across in courses I've purchased on Udemy. If I use one laptop or computer with one monitor, everything runs fine and easy as cake. However, for a long time, I've had an issue with Udemy where if I have an external monitor connected (a 27-inch Dell monitor), I cannot use it because the current course video is completely blacked out. I can't see anything on the screen, but I can hear the audio, like in the image below:

The solution

There are two solutions that we can use to solve this

1. Lower the refresh rate of your monitor to 60Hz if you have set it up to 120Hz or higher. Alternatively, you can lower it to 60Hz too.

2. The second solution that worked for me was disabling hardware acceleration on Chrome.

   1. Go to the three dots in the upper right corner of Chrome, then go to Settings.

1. Toggle the option of hardware acceleration off.

2. 

   Then, restart your browser, and you are done!

Happy Study time! I hope it was helpful :)

Main sources
- Reddit & Secod Reddit conversation