Non-Indexable Page Inlinks Only
What This Means
Indexable pages that are only linked to from pages that are non-indexable, which includes noindex, canonicalised or robots.txt disallowed pages. Pages with noindex and links from them will initially be crawled, but noindex pages will be removed from the index and be crawled less over time. Links from these pages may also be crawled less and it has been debated by Googlers whether links will continue to be counted at all. Links from canonicalised pages can be crawled initially, but PageRank may not flow as expected if indexing and link signals are passed to another page as indicated in the canonical. This may impact discovery and ranking.
What Triggers This Issue
This issue is triggered when indexable pages are only linked to from pages that are non-indexable, including those marked with noindex, those that have been canonicalised to other pages, or pages disallowed by robots.txt. For example if a page on the following website: https://www.getasky.com/page1/ Was linked to from one page: https://www.getasky.com/page2/ But https://www.getasky.com/page2/ had a meta noindex tag.
How To Fix
Ensure you link to important pages from indexable pages to avoid any uncertainty in discovery, indexing and ranking. Consider whether the non-indexable pages linking to these pages should be non-indexable.