Take into account that a traffic drop explanation may not be displayed in Google search console. That’s why there are several things to check.
The issue may be related to the DNS resolution of names. This can be related to the misconfiguration of the DNS server. That’s why it is important to check the DNS queries, the HTTP server answers, If you website sits behind cloudflare, it is not likely to be the DNS server since cloudflare is the DNS server.
Some firewall may rate limit access to your website. They also may block googleBot. That’s why you should check the logs of your firewall. Also, it would be important to check that no configuration files block googleBot (like a htaccess file). To verify that googleBot can visit your website, go to your Google search console, click on “fetch as google” and then, on “fetch and render”. If the status is “complete” or “partial” after the scan, it is perfect, otherwise, there is an issue related to your web server.
Web server misconfiguration
I must say that today, this eventuality is rare because the server always return an error in its log or it is displayed on the screen when trying to access the website.
I saw so many wordpress plugin who blocked googlebot and thinking about it is scary. It is really important that you install wordpress plugins that you understand. Disable any plugin features when you aren’t sure about the effect it has on your website. WordPress plugins are almigthy. They can block a visit from a Google bot. They can return a 500 server error from some pages and you may not aware of it. They can slow down the pageload without you being aware of it. They may return a different content for Googlzbot and for a regular visitor triggering a Google penalty. Many different wordpress plugins may explain a traffic drop. That’s why it is always better to have the smallest number of WordPress plugins on your installation.
There are many possibilities when the issue is related to SEO. For example, a page can be a duplicate of another webpage on the Internet. There are maybe several webpages with the same title. I also found that many numbers in the title of several pages were responsible for a penalty. It could also be outbound links that pointed to spammy websites.
It is also often a canonical issue. For example, a HTTPS can be accessible from a http URL, https URL. If there is no canonical tag, Google may not know which URL to choose. That’s why it is important to add 301 redirects to your web server.