We often miss all the ways animals right here on Earth try to get our or each other's attention.
A truly alien species might communicate in ways we cannot even detect, or think of detecting, like say magnetic fields or some other medium that almost nothing on Earth uses.
Furthermore, even if they used the same "channels" and frequencies as us, their minds may just be too different. Even fundamental concepts like time and numbers or the notion of self may be perceived too differently by them for their languages to have any convenient analogues to ours.
A truly alien species might communicate in ways we cannot even detect, or think of detecting, like say magnetic fields or some other medium that almost nothing on Earth uses.
Furthermore, even if they used the same "channels" and frequencies as us, their minds may just be too different. Even fundamental concepts like time and numbers or the notion of self may be perceived too differently by them for their languages to have any convenient analogues to ours.