The main issue appears to be, as ramoneb pointed out in his thread, the MISO and MOSI lines of the MMC are incorrectly switched.
The clue is the logic contention (
yellow indicator) on the MMC DO pin.
View attachment 81542
Once the lines are switch, your code yields the expected results, no led lit indicating the card has been successfully detected.
View attachment 81543
The labeling on the MMC is obviously in reference to the Master device rather than the Slave device.
BigDog