It's already a very good sign that the beep generator works. The beep generator is implemented in the digital domain which means that the DACs must work in order for you to hear a beep. Therefore the DAC configuration is ok.
The VOL/MICDET pin can be configured as an analog input to a on-chip SAR ADC, which in turn can control the digital volume before the audio is converted to analog. This makes it possible to use a potentiometer connected to the VOL/MICDET pin as a vintage style volume control.
If you do not use the VOL function but want to use the MICDET function, the SAR ADC uses the voltage on this pin to determine if a headset was inserted. If no headset (or microphone) is detected and you connect the MICDET pin to the resistor after MICBIAS, the SAR ADC will see a voltage equal to MICBIAS and "know" that no microphone is attached.
Once a microphone is attached, it'll pull the voltage that the SAR ADC sees lower than MICBIAS (but not to ground) and the internal detection logic knows now that a microphone is present.
If a push-button is depressed (shorting the microphone), the SAR ADC sees zero volts and the detection logic detects a button press.
If the beep works but the DACs don't play back audio from the I2S interface, please check the I2S interface settings and the I2S signals on your board with a scope (attach a screenshot showing all I2S signals).