I would hazard a guess your hormones weren't as concentrated despite it seeming to be a decent hold, and this is why. Also, despite line lists declaring a specific threshold, they do seem to be able to detect lower amounts so my guess is your pee has to meet that minimum for it to turn it positive, whereas a line test you're able to see faint lines there which may be faint because of a slightly lower level than the threshold. Does that make sense?