Why has my startup chime stopped working on my MacBook Pro?

Welcome!

What year is your MBP? Please see:

About Mac startup tones - Apple Support

including this bit:

Mac models from early 2016 and earlier make a chime sound when they start up. Mac models from late 2016 and newer don't have a startup chime, with the exception of MacBook Air (13-inch, 2017).

Which exact model is your MacBook Pro? Apple notebooks, since late-2016, no longer make a chime sound when starting up. The exception is the 13-in 2017 MacBook Air.

Ref: About Mac startup tones - Apple Support

Does your notebook provide any sounds from its internal speaker, not just not providing the start up chime?

Ok, thanks for clarifying which MacBook Pro model you have. I am then assuming that the startup chime was working before ... correct? If so, then something may have disabled it.

You can re-enable it by using the following command in the Terminal app: sudo nvram -d SystemAudioVolume

Note: Using sudo will require that you know the Administrator password for your notebook.

debbyj wrote:

I don't even know where to find the Terminal app, much less know what to do once I get there. And is my Administrator password the same as my password to turn on my computer?

You will find the Terminal app in the /Applications/Utilities folder. You would run it like any other app. When it runs it will open a window with a command prompt, similar to a DOS prompt ... if you are familiar with DOS. Regardless, you would just enter the command string I provided you, and then, press the return or enter key. Again, if it asks you for a password, you would use the same password you used when you first set up your notebook.

Finally, to close the Terminal window, enter exit at the prompt, and then, press return.

Great! I'm glad you got things working again.