It won't run in dual channel mode with 3 sticks of memory, but I don't think that is your problem here. 3 sticks will work just fine in single channel mode. Look for something in the BIOS called "memory remapping" or something similar. If you have the option, then check to see if you have "software remapping" and "hardware remapping". If you have both, enable hardware remapping, if you have don't have a choice, then just enable remapping. Older boards sometimes had this feature and you had to enable it to remap memory above certain addresses or you couldn't use all of it.
But please continue to do what you are already doing by testing each of the sticks to make sure they all work by themselves, and you have them in the correct slots.
Yes the sticks are all correct ive test them all