No me di ni cuenta

No me di ni cuenta
 

No me di ni cuenta

Which is a more correct translation?
I didn't even notice or I didn't notice at all.

I got it from a song and the lyrics goes like this.

y al llegar la mañana
no me di ni cuenta
de que ya nunca estabas.

Both of your translations mean the same thing to me, so both are correct. 'I didn't notice at all' is used less, for what it's worth.

Why notice and not realize? Both ni and nunca are used for emphasis meaning "I noticed you weren't there but I didn't realize you were gone for good"

It depends on the context, whether you need realize or notice: OED for dar cuenta:

Cuando la frase darse cuenta va seguida de una oración subordinada introducida por de que, en el español latinoamericano existe cierta tendencia a omitir la preposición de en el lenguaje coloquial - se dio cuenta que no iba a convencerla = he realized (that) he wasn't going to convince herdarse cuenta de algo to realize something; lo hizo/dijo sin darse cuenta he did/said it without realizing; ni se dio cuenta de que me había cortado el pelo he didn't even notice I'd had my hair cut; date cuenta de que es imposible you must see o realize that it's impossible; ella se da cuenta de todo she's aware of everything that's going on (around her); ¡eso me contestó! ¿tú te das cuenta? that's what he said! can you believe it o can you imagine?;

Thanks for the input everyone. What is OED?

Sorry, my mistake. I typed OED for Oxford English Dictionary, but actually meant GDO: Gran Diccionario Oxford (English-Spanish) (It comes with a CD and you can load it on the computer and use it as a cut-and-paste as I did above.)

Thank you.

In the context of those lyrics the meaning is ambiguous, but it refers to something exclusively perceived with the mind.