What triggers the issue?
This issue reports pages that are only linked via a redirect.
Why is it important?
If the destination page has no incoming internal links, it can’t be reached in any other way other than through the redirect.
How to fix it?
The issue concerns only indexable pages that you actually want to be ranked. If a reported page doesn’t meet that criterion, you shouldn’t worry and can simply ignore it.
In case those are indexable pages, study closely why the destination pages don’t have any incoming links. For example, if you recently moved your site from HTTP to HTTPS, it stands to reason that your old links will go to the HTTP version first and then redirect to the HTTPS, hence, no direct internal links. To solve this problem, change the links on the referring pages so that they point to the HTTPS page directly.
Generally, it is recommended to audit your site and check your link infrastructure. Make sure that your relevant pages can be easily found.