Ah… of course! Sorry!
I’m going to apologise in advance because I’m about to ask you a lot of questions but this is just so I can better understand what’s going on in your setup and how we can fix this 
On the first page of this thread, you have the Sound Wave type added - what’s updating this?
In your screenshot on this page, you have the Get Audio node - how is that being updated? It looks like it’s separate from the Structure and that might be why it’s only playing one sound or only playing once - how is this Get Audio node getting updated with a new sound? (If it was an Array it could have multiple values, but if it’s not it’ll just have one value. If nothing’s coming through to update the Get Audio node elsewhere in your BP when you flip to the second line of dialogue, this could be the problem.)
How are you calling your Structure data from within the BP? Using the Get Data Table Row node will call all of the columned data on a specified row and might be the best solution.
How do you have your structures and tables set up? I can see 4 different Structures on your page 1 screenshots - are they all unique or are they controlled by a master Structure? Just trying to get an idea of how big a task you’re dealing with
I think the simplest solution is to store the audio within the Structure itself by adding a type Sound Cue and assigning cues to each line of dialogue in the table. That would use your existing setup.
Alternatively, depending on how much work is involved for you, if you had an independent Structure containing all the dialogue, text, character names, locations… whatever you need to use for each quest/area/character or whatever works for you, then you can use the Get Data Table Row node in a BP to call all of the data stored in that row of the Structure. That would include the corresponding Sound Cue, which you can hook up to a Play Sound 2D node (or Play Sound At Location, if you need to have it coming from the NPC).
For Data Tables, Enums, etc. check out Mathew Wadstein’s YouTube: https://www.youtube.com/channel/UCOV…bRdVEm0hONTrNQ