CardInfo example fails - can't use SD card

So I just bought a Mega2560 board and an SD card module. I connected pin 50 to MISO, 51 to MOSI, 52 to SCK and 53 to CS, then set chipSelect to 53 in the CardInfo example. I connected VCC to 3V3 and GND to GND, inserted an SD card and tried it. It only shows:

Initializing SD card...initialization failed. Things to check:

  • is a card inserted?
  • is your wiring correct?
  • did you change the chipSelect pin to match your shield or module?

I have tried the same with another card, rewired everything and checked that the card is receiving the proper voltage. Nothing worked.
I tried this after failing to interface the SD card at a very low level, i.e. writing to SPxR. Set CS to HIGH, sent 10 dummy bytes, set CS to LOW, then sent CMD0 to the card, which only responded with 0 every time, entering an infinite loop. The time that CardInfo took to give the error suggests that it was the result of the very same problem, caught with a timeout counter.

May it be the case that the SD card shield does not function properly? If so, how could I make sure before ordering a new one? Thank you in advance!

Never mind. Apparently this particular shield required VCC to be connected to 5V, even the instructions recommended 3V3 but allowed 5V. Now it works. Thanks anyway!