What are you trying to achieve? Could you share any reference images?
To use Flowify, it’s not necessary to work with solid objects, so there’s no need to check with the solid inspector. However, your wavy wall should be made of a clean quad mesh. If you created it using Corviloft, it should be fine, as long as the "top and bottom" and "left and right" curves have the same number of segments. Flowify requires quad geometry, not solid objects. You can verify this by turning on the hidden geometry.
For additional guidance, you can follow this Flowify tutorial:
https://www.youtube.com/watch?v=zCFUCE7Bb4Q