GSC 4xx error - Traffic Down To Zero | What to do?

One of my clients has a niche site that was getting around 100 visits per day.

But the traffic suddenly droped to almost zero in the past week.



No any position droped on serp. No keyword drops. So I assume this is a technical issue. But I cannot find what pages to fix.




The links look like below on GSC. But not loading only blank pages.



What's causing this issue. I checked for 404 errors on the site using RankMath plugin. But did not find any.

How can I diagnose this issue? What can I do for this.

That looks to me more than 4xx error - it is related to Spam update.

There was massive Google search Spam update released last week.

You want to read more about that.

I don't the issue is the 4xx error, Google won't give a warning on 17th then make you loose it all, I think this has to do with the SPAM update.

When exactly did the drop start?

The timing makes me think it's the spam update