A page that looks complete to a customer can appear blank to Google — and every page Google struggles to understand is an opportunity for a competitor to earn that click. JavaScript is often the culprit: Googlebot reads standard pages immediately but returns days or weeks later to process JavaScript, pushing product updates and new content out of search results longer than most business owners realize. How a website delivers content matters too — client-side rendering asks Google to build the page after it loads, while server-side rendering delivers a finished page ready to be processed. When a full rebuild isn’t realistic, dynamic rendering protects search visibility by providing search engines with an easier version to crawl, while customers see the same experience. Warning signs include slow indexing, updates missing from search results, and ranking drops after a redesign — all signals that Google may not be seeing what visitors see. The right fix depends on how the site is built, and an SEO agency can identify rendering problems and prioritize solutions before the traffic gap widens further.

source: https://www.seonational.com/why-google-cant-always-see-your-website/