Weak battery at 12V
I've experienced a 12 V battery that was charged enough to run the starter motor but obviously not enough to feed the sparks. The engine could then not crank.
Source: Diverse

Quick facts
Healthy battery shows a 12,6 to 12,8 volts charge. To fully charge a battery it requires 7.5 amps for 36 hours. Longest battery life is at 95% charge, not 100%.
Source: Diverse

Battery operating voltage
Car turned off à multimeter connected to the battery should read 12.4 volts which is 25% discharged.
12.2 volts is 50% discharged.
When the starter is activited it should drop to 11 but not less than 10 volts. Under 10 volts the battery is discharged.
Source: Diverse