"Why did he not speak to her on the phone?"
Translation:¿Por qué no habló él con ella por teléfono?
why not a ella? I was so pleased with myself for having remembered the personal a.
Very good, ¿Por qué él no le habló por teléfono? would be a correct translation of Why did he not speak to her on the phone?, (and my guess is that DL will even accept it with "a ella"), but you need to use the "le" in that case
Why "¿Por qué no le habló por el teléfono?" is incorrect? It says I missed the world "él", but I have known that in Spanish you don't need to write the subject pronouns.
I did that way, but I don't know why the translation Duo gave works. Can someone explain it to me please?
Habló with the accent is third person/formal you simple past. Hablo without is first person present tense.
Don't know if I've ever seen hablam before. What is needed is just the simple past tense.
¿Por qué él no la habló por teléfono? DL tells me it should be le but la I thought to her should be la?
I made the same mistake. It should be 'le' because 'to her' is an Indirect pronoun; while 'la' is a feminine Direct pronoun. http://spanish.about.com/cs/grammar/a/objectpronouns.htm