This might be due to an occasional "weirdness" in Soundflower that we've seen a few times over the years.
Sometimes, sound flower can seem like it's volume levels are up (at 100%), yet it's muted. The fix is to go through Audio Midi Setup, and change all values on the input / output sides of the device.
Audio Midi Setup
AMS (Audio Midi Setup) is an app provided by Apple.
You'll find it in the Utilities folder, or simply use spotlight.
Trying the Fix
Please see the following video of how to change the soundflower values in Audio Midi Setup.