I can't bleach my black euro next Remy human hair extensions? help appreciated!?

So, today I tried to bleach my hair extensions with very little effect. I used a basic white bleach with 30 volume creme developer. I applied it on my extensions and I waited half an hour and every so often during that half an hour I would check if the bleach was working. However; to my dismay, it did no effect whatsoever! It's still black.. the same as before and if it counts only two strands became a blond tone. Was there something I did wrong? or any steps that I didn't include? if anything, I will appreciate any kind of tips or advice! :) thank you all very much! :D