Using the "validate fix" button within Google Search Console to communicate to Google that you fixed an issue, does not signal to Google to expedite anything on its end. It just a reporting mechanism for you to track when Google recrawls the issue and for you to see if it was "fixed" according to Google or not but it does not speed anything up.
Google's John Mueller confirmed this in a Reddit thread, when he said, "The "mark as fixed" here will only track how things are being reprocessed. It won't speed up reprocessing itself."
So if you think clicking that validate fix button will make it faster for your issues to be reprocessed by Google, it won't. You can request Google to recrawl the page through the URL inspection tool, to try to speed things up, but the validate fix won't do that for you.
Here is the validate fix button in Google Search Console for page indexing issues:
Here is the email you get after you click it:
Now, with 404 pages, I do not expect these to be marked as fixed. I want most of these pages to 404. In fact, when I did the redesign of this site, I set a lot more 404 pages up for a lot of funky URLs because those pages should not exist. That being said, Google will still tell me they are 404ed and that is fine.
John Mueller when on to write:
The "mark as fixed" here will only track how things are being reprocessed. It won't speed up reprocessing itself (also, it's unclear what someone would want by marking 404 pages as being "fixed" - so it's really just for your own tracking).If these aren't meant to be 404 - the important part is to fix the issue though, set up the redirects, have the new content return 200, check internal links, update sitemap dates, etc. If it hasn't been too long (days), then probably it'll pick up again quickly. If it's been a longer time, and if it's a lot of pages on the new site, then (perhaps obviously) it'll take longer to be reprocessed.
If they are supposed to be 404s, then there's nothing to do. 404s for pages that don't exist are fine. It's technically correct to have them return 404. These being flagged don't mean you're doing something wrong, if you're doing the 404s on purpose.
Forum discussion at Reddit.
Update: John posted an update for us saying, "Just to keep you on your toes, there are *some* situations where we do expedite crawling based on 'validate fix', for example SD / AMP issues (where a fix is recognizable). I'm double-checking with folks for the details though."
