Hi Kacie,
The issue that you’ve encountered with the Volume bar can be caused by a software conflict. To isolate this concern, we suggest that you perform a
clean boot. This will help us determine if there are third-party applications that may be causing it to stay on the screen. Please click
**here**for the steps.
Once you’re in the clean boot environment, try to turn the volume down and it will allow you to do so. If you’ll encounter the same result, then, it could be that a has already occurred.
Note: After the troubleshooting, refer to this section: “How to reset the computer to start normally after clean boot troubleshooting*” on the same* support article to boot the computer in normal setup once the issue has been resolved.
We'll wait for your update after trying the steps.