To diagnose it, click the "More Info" tab in the URL Inspection Tool.
A single error in your JavaScript code can stop Google from rendering, which in turn can make your site unindexable.
Your site may work fine in recent browsers, but if it breaks in older browsers Google’s web rendering service is based on Chrome 41, your Google rankings may drop.
Need some examples?
A bug in the official Angular documentation was causing sweden mobile database Google to fail to render our test Angular site.
Some time ago, Google removed some pages of Angular.io, the official website of Angular 2+.
Additional note: If you don’t want to use the URL Inspection tool to debug JavaScript errors for some reason, you can use Chrome 41 instead.
Personally, I prefer to use Chrome 41 for debugging purposes because it is more versatile and flexible. However, the URL Inspection Tool is more accurate in emulating the Google Web Rendering Service, which is why I recommend the URL Inspection Tool to those new to JavaScript SEO.
Step 4: Check if your content is indexed in Google
It’s not enough to see if Google can render your site correctly. You have to make sure that Google has indexed your content correctly. The best option is to use the site: command.
This is a very simple and powerful tool. The syntax is very simple: site:[URL of a website]"[fragment to be searched]". Be careful not to put a space between site: and the URL.