Good Afternoon aneeshsoni,
We see that you're looking for assistance with an HDCP error while using an external monitor, and we'd like to see how we can help.
Just for clarification, if you were to play the video on the MacBook Pro screen with the monitor still connected, do you still get the message? Also, have you checked to make sure you're updated to the latest supported macOS version? If you're unsure, take a look at the following resource for help with that.
Update macOS on Mac
If you do see that there is an update available, be sure you have a recent backup of information just to be safe. For help with creating a Time Machine backup, take a look at the next resource:
Back up your Mac with Time Machine
If you see that an update isn't applicable or helpful with your situation, let's see if you're able to use another HDMI if you have one. If you see that a different HDMI cable clears this up, we'd recommend looking at replacing the one that you're currently using. Also, try connecting with a different monitor or TV if that is an option just to see if this is isolated to the Samsung monitor that you're using.
Lastly, this can occur at times if your Mac goes to sleep while a video is playing or paused. If this is when you notice the error, you'll want to quit the app and open it again to clear that up. For more information on this, take a look at the section labeled "After making the connection" of this resource:
Connect to HDMI from your Mac
We hope this information is able to help.
Have a great day!