When it stays dark
Five things a TK52 does when something is wrong, and what each one means: dark with the sketch running, random dots, every LED on, a picture on its side, and a board that dims or resets when the picture is big.
Five symptoms
Dark with the sketch running. The MAX7219 powers up in shutdown, display blank, and stays that way until something writes 1 to register 0x0C. If the sketch does, the supply is next: VCC on 3V3 is under the chip's 4.0 V minimum.
Random dots. The bits are landing in the wrong registers. DIN and CLK swapped does this. On a 3.3 V board, the thin margin on a HIGH can do it too. A clock wire on NC, the pin beside CLK, does not: with no clock nothing goes in at all, and the display stays dark.
Every LED on, full brightness. That is display test, register 0x0F. It overrides everything else, the shutdown register included, until it is written back to 0.
On its side. The rows went in as columns, or the board disagrees with the
book's drawing. TURN in the sketch turns the picture in quarter turns.
Dims or resets with a big picture. All sixty-four at level 15 is about 330 mA from your board's 5V pin. Lower the level, or give VCC a 5 V supply of its own with the grounds joined.
A test that needs no picture
Write 1 to register 0x0F. Every LED lights at full brightness if VCC, GND, DIN, CLK and CS are all right, whatever the other registers hold. Write 0 to turn it off. If display test lights nothing, the fault is in the five wires, not in the sketch.
When it does not work
Then the chip has not been woken, or it has not heard you. Check the sketch writes 1 to register 0x0C, then check CS: a CS wire on the wrong pin means no message ever takes effect, and the display stays exactly as it powered up, blank.
The chip forgets everything when the power goes, and powers up asleep. The sketch has to run again from setup() after every power-up, which it does on its own when your board restarts.
Draw the picture with every bit set and look for the gap. A whole column dark points at the matrix or its soldering; a single dark LED is usually the LED. Display test, register 0x0F set to 1, lights all 64 for a quick check.
VCC is probably under 5 V: on 3V3, or on a long thin cable from a weak USB port. Measure VCC to GND with a multimeter while it is lit; the chip wants at least 4.0 V.
The pin table, the specifications and the files for the TK52 and the 3-pack.
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