My external monitor speakers are not showing up on my MacBook Air

After traveling and using my MacBook Air (M1, 2020, Sequoia 15.5) using both the built-in speakers and headphones for Zoom calls, I can no longer access the speakers in my external monitor (HP E27m G4 QHD)--they no longer appear in the "Sound" pull-down menu in my Mac's Settings. The HP speakers worked perfectly before now. The monitor's webcam is still working with my MacBook--only the speakers are offline. Help?!

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