Gee I remember tinkering an intercom using an MPA-40, some 30 years ago... it has no "mic out" connector. You can use the voltage-reducing resistor between the GND and the 4 ohm out signal, independently of which other connection the speaker uses.
Also, TEAC says that the recorder only records on these more expensive CDs that are labeled "for audio recordings", because of copyright issues. I don't know if it can still do it on regular CDs, or if it really does check for some ID from the blank disk, so if you still get no sound it may be one more thing to verify.