A weird thing I found was that if the array size is over around 400 (it’s a float array), then the whole thing just doesn’t work. There’s no error message or anything, just nothing happens. It can’t be because there’s not enough space on the arduino board – a way bigger array should still easily fit, plus the IDE would tell me if this was the case anyway.
In Flash, yes. In SRAM, no.
You need to take explicit action to keep the array in PROGMEM (Flash), which you are not doing. Not that it makes any sense in your case, since flash memory is read-only.