I’d guess he’s given you 14g and you have a fancy lightweight 15g wheel. Or you have a more normal 14g and he’s given you some fat 13gs. What spoke key fits? Have you measured your spokes (near the thread) with a caliper?
It transpires that most of my nipples were correct. However I have three spokes that are narrower…guess which nipples broke? Guess which spokes I was then trying the replace the nipples on, to no success./