Hello Erica,
I think the “not plugged in” Realtek entry may refer to the 3.5 mm headset microphone jack, not necessarily the built-in microphone. The built-in microphone should normally appear separately as Microphone Array.
This might involve the Intel Smart Sound Technology/Realtek driver stack. Please check:
- Open Device Manager and expand System devices.
- Look for Intel Smart Sound Technology OED.
- Check whether it has a warning icon or shows Code 43 under Properties > Device status.
If Code 43 appears, I would suggest you download and install the audio driver package for the exact A515-57 submodel from Acer website.
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