Memory is guaranteed in the form sold. Buying memory by matching part numbers up carries no guarantee to be compatible.
The extra stress on the memory controller caused by adding extra memory could cause the PC not to boot or the original memory to no longer be able to operate at rated specifications. That is, your original memory was 2400MHz now may no longer be able to operate above 2133MHz or may not boot at all.
Your statement that, "AsRock motherboard is incapable of taking 4 sticks of 8 g memory at 2400" is false. Your problem is caused by adding extra memory that has never been tested together with the old memory and has no guarantee to be compatible with your old memory.