Here is the information about my MP3 file. Upon testing, it seems that the mpv player is unable to play audio with a sample rate lower than 40kHz or audio with a very low bitrate.
Audio
Format : MPEG Audio
Format version : Version 2
Format profile : Layer 3
Duration : 1 s 608 ms
Bit rate mode : Constant
Bit rate : 32.0 kb/s
Channel(s) : 1 channel
Sampling rate : 24.0 kHz
Frame rate : 41.667 FPS (576 SPF)
Compression mode : Lossy
Stream size : 6.28 KiB (74%)
Writing library : LAME3.100