For a number of months now, some Google cache links on search results pages have served 404 page not found errors when clicked on. While Google confirmed that this mobile-first indexing cache bug didn’t affect the site’s ranking, that didn’t stop webmasters from being concerned.
Cached page: Unfortunately, it looks like we’re currently still not showing a cached page for many mobile-first indexed sites. This is a bug, not by design, and should get resolved over time. It’s just the UI, it doesn’t affect crawling, indexing, or ranking.
— Google Webmasters (@googlewmc) June 14, 2018
Google rolled out a fix this weekend that resolved the issue that was causing the cache link to serve a 404 page.
It hasn’t been confirmed by Google yet if they it was fixed fully.
When the bug was still active, you weren’t able to view the cached version of your web page from the Google search results. The following is a screenshot of the error that folks were seeing: