Low RMS levels

That actually doesn’t appear to be that far off (although it could use work).

You’re using ACX-Check, but are you using the rest of the Mastering Suite? We are warned against using these tools in isolation. They depend on one another for proper operation.

https://forum.audacityteam.org/t/audiobook-mastering-version-4/45908/1

It goes for pages, but it’s basically only three corrections: Rumble filter, Loudness (RMS) setting and overload prevention (Limiter).

If your voice is even close, that should get you past ACX-Check, and even if you miss noise (most home productions miss noise), that may be helped by Noise Reduction.

You have to download and install RMS Normalize. I think you already have everything else assuming you’re using Audacity 2.2.1.

As for recording, I’d be surprised if you didn’t have to run the volume controls all the way up, and possibly get closer to the microphone. Most home devices have “gentle volume.”

You don’t have to guess at your recording volume. Look at the bouncing sound meter and the blue waves while you make a test recording. While you’re recording the meter should bounce between -10dB and -6dB. The blue waves should poke up about half-way or a bit less.

In general you should be about a Hawaiian Shaka away from the microphone.

If you have a blast filter, about a power fist.

You are the recording engineer so you get to worry about all this stuff. They don’t tell you that when you’re buying the microphone.

Koz