This question&answer is a cross-post of one of my posts on Reddit.

Since the introduction of CreationKit 64bit for Skyrim Special Edition, the in-built tool to generate sound files did no longer work within the response tab of your dialogue. Technically, you cannot directly take records during a CK session, and the result is that scenes and dialogues break and do not show up properly in-game.

This is what you can do:

1. place a folder with a dummy file. Use the Stock\_1.fuz from fuz roh doh download. Data\Sound\Voice\(yourmodname.esp)\(yourvoicetypename)\ the ID of the voice line you read in your response-FuzRohDoh: Fuz Ro D-oh – Silent Voice

2. get this dummy file automatically inserted by Fuz Roh Doh, will work for LE, SE and AE if you have the most recent SKSE. You could avoid AE by downgrading your AE to SE again. Downpatcher: Unofficial Skyrim Special Edition Downgrade Patcher (Note that you can apparently now use FuzRohDoh again for AE since 09.01.2022, I did not test it yet.)

3. record in legendary edition with the tool provided in Creation Kit.

It is suggested however to use 1 or 2 for dummy files and later replace them with high-quality mastered voice records. Usually, voice actors are happy to support you, and some editing can really help to normalize the files and remove unwanted hall effects and other noise. Alternatively, you can use the voice line generator tool, which is surprisingly well working. If you are interested, have a look at the detailed tutorial for using xVASynth here: Auto-Generate Voice Lines using xVASynth

References:

Disclaimer:

1. I do not take any responsibility for missing files or broken games, I just share the approach in best faith, with the goal of helping you to find the solution yourself, at your own risk.
2. Thank you to everyone working with me on Creation Kit contents, especially Elscrux, Thingy, and Jani. This is mostly a fix for starters, anyone who knows their way around CK is probably aware of this method by logic.