No volume at all from calls

My Moto E (Tracfone) worked fine for many months. Now, I hear nothing during calls. When put into speakerphone mode, all is well. Also, plugging in earbuds works well. I do get normal volume from message alerts, ring tone, etc.

Perhaps another app has disabled audio for the "normal" (non speakerphone) case? How to identify the culprit?

Chuck

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