Searchmetrics does not show a ranking for a keyword even though it actually ranks at the lower position? This is because the Searchmetrics Suite lists all keyword positions up to the 5th results page, i.e. all rankings up to and including position 50.
The reason for this restriction is that rankings after position 50 have no significant influence on SEO and have very little chance of generating traffic.
If these keywords are to generate traffic, they must be optimized. For example, a technical analysis can be started in the Site Experience to find technical optimization potential. Or you can directly create a briefing on the topic to optimize the content
The rankings from 1 to 10 still bring the most traffic, so you should always try to optimize on these positions to generate as much traffic as possible.
It is also worthwhile to find "Low Hanging Fruits", because they have a good chance to be on the first result page.
If you want to know more about ranking factors have a look at the Searchmetrics Ranking Factor Studies.