I anticipate you're going to get a lot of responses, some that are not informed.
Use the site search for SN successes and failures, there's a regularly updated thread that's gathered all of them that have been reported on the site. It is one of the most informative reads on the method. Someone may link it here, it's too much effort for me or I would.
As long as the SN is strong enough (over 95% pure, and I advise you test it, there are threads about blood testing and aquarium test strips), and you take enough (20-25 g in 50 ml water), and not too much (which could cause you vomit too quickly), and you fast properly (see Stan's guide), then it will work. If you take it and vomit, it will still work, it's immediate vomiting that would be a problem and you've got to screw up to for that to happen.
No one has ever reported synthesizing it, period.
If someone takes too little or it's not pure enough for fatal methemoglobemia, then they're really, really sick.