If you login to Google Search Console and check out the coverage report, you will see a notice about another feature that Google has temporarily disabled. Google posted "issue validation is temporarily disabled due to upcoming changes in the report."
So if you want to use the "validate fix" button for issues you resolved around your crawling errors, you might be out of luck for now.
Google explained this in more detail saying "if you see a "validation temporarily disabled" message in your report, this is because we're updating some of the criteria for some issues in this report." Google clarified that "this change does not affect validation requests that are currently in process, but new validation requests can't be submitted until after we finish updating our issue criteria."
Here is the notice:
Now not only is the request indexing tool temporarily disabled but now this validate fix feature is also temporarily disabled.
Forum discussion at Twitter.
