Hi ach2166,
Thank you for reaching out to Apple Support Communities.
We see that you have an issue with taking a screenshot on your MacBook Pro. You have reviewed the Take a screenshot on your Mac resource. We want to help. Those keys should work together for you to take a screenshot. You can try a couple of resets. Neither will affect your data.
You can reset the SMC. Here’s How to reset the SMC of your Mac - Apple Support
If that doesn’t help, please reset the NVRAM. Here’s how to Reset NVRAM or PRAM on your Mac - Apple Support
If neither reset helps, test in safe mode. Here’s how to How to use safe mode on your Mac - Apple Support
Here are a few quick notes about safe mode:
- Safe mode often looks and responds a bit different than what you're used to.
- Safe mode does not load everything that normally loads during a regular startup.
- Safe mode is a bit slower while loading and during normal operation as well.
- These differences can be cleared-up by a normal restart.
Test to see the issue happens in safe mode. Restart and test again in typical mode. Just booting into safe mode in and of itself can resolve some issues.
Hope that helps.
Best Regards!