What do you mean when saying the power cables keep falling out? Aren’t they firmly connected to the hard drives? If the drives are not getting enough power they will not be recognized by BIOS or the Windows installation software.
Please try with only the SSD connected. Is it recognized? Reset BIOS to its default settings and try again. Could you please send us a picture of your motherboard with the drives connected? If you have the option, please test one of the drives in another PC just to confirm that they are working normally.
Hope this helps