Been there, done that, it was a failure, and the spoke nipple is not happy about it. It does not fit spoke nipples.
OK, maybe it's a badly designed spoke wrench??.......whatever it is, it sure looks like it's meant to turn something kinda small with flats on it. Spoke nipples seem to be the first choice when I saw the pic.....or maybe a centerpull brake stirrup cable puller??......A tire valve remover??.....There are different sized spoke nipples out there too, maybe you tried it on one that's just too small or way too big?
Chombi