Trying to use sound flower to record Internal Audio on Catalina, But I'm just getting a flatline. What should I do?

[kozikowski]

What should I do? is it because I updated to Catalina?

Yes.

Catalina carefully peeled off all older 32-bit apps as they were warning it was going to do. If it’s critical that your older software keep running, you could roll back to the earlier Mojave, still, as far as I know, still supported.

Also see:

Problems recording samples from Spotify on macOS [SOLVED]

That is extremely old / obsolete, and in my experience it’s not very stable on modern Macs. There’s a much newer version called “iShowU Audio Capture” (Note this is not our product and we don’t provide technical support for other people’s software, but here’s the link: https://support.shinywhitebox.com/hc/en-us/articles/204161459-Installing-iShowU-Audio-Capture)

Koz