Flint, as a computer brain, is still learning and so hasn't yet perfected keywords and content recommendations for every industry.
If you are notified your industry is not one of the industries Flint's ready for and you want to use Flint anyway, we'd suggest that while Flint is still learning, you use a keyword phrase you are more confident with from doing your own research e.g., through tools like Google Keyword Planner or simply asking your customers what they search for in Google when they find your business. You can also learn more about optimising your website for search engines in Rocketspark's SEO help guides.
Once you've confirmed your keyword phrase and you've put it into the keyword phrase field, you can continuously use Flint to assist with generating your meta tags and web page content.
Learn more about how to use Flint in the help guide Flint (Rocketspark new SEO tool) FAQ.