Weird. Heard people respond differently. Maybe you are one of those people who dont really get euphoria from opiates. Well the fact that you are naive to kratom and were able to handle 15gr is pretty incredible. I'd say try half the dose. Take magnesium with it, some fruit/salt/electrolytes and dont dry out.. Maybe it was crap kratom, idk. Super green seems to do the job for me lately Go complain if you want, I kinda do think their red strains are weak at the moment .. not sure, hard to tell