Is the Source Track Indicator pointing to the same Targeted track?
Thanks for that pointer! everything is solved now. Now I don´t mean to abuse but could you explain a bit what´s that A1 Source thing and why does the audio has to go exactly in that track?
The A1 thing is the Source Track Indicator. That's what let's you know that the clip currently loaded into your Source Monitor has an audio track, and that it's scheduled to go into the "Audio 1" section of your sequence, so long as "Audio 1" is also Targeted. (Both need to be a lighter shade of gray.) If you want to Insert/Overlay video without audio, you can turn off the A1 (make it dark gray) so that only video comes down. If you want to put audio on 2, you click and drag the A1 down one box, then Target "Audio 2".
As a side note, you will notice that if you load a clip into the Source Monitor without audio, A1 is missing. If you load an audio clip into the Source Monitor, you will notice the corresponding V missing.
Awesome, thanks a lot!