iHola!
Could you please clarify the point:
No se marcha porque está cansado (No se marcha y la causa es que está cansado)
No se marcha porque esté cansado, sino porque se ha enfadado (Se marcha y la causa no es que está cansado)
I've come upon a sentence:
No vino porque no quisiera, sino porque no pudo (The translation says: He did not come not because he didn't want, but because he could not)
So I wonder if it really says that somebody didn't come. I guess one "not" is missing
Regards,
Alexander