🇮🇳India Jegan2668 Bangalore
I too faced the same issue when updating the version from 4.0.0 to 4.0.1. But, no error logs displayed in backend and tried clear caching by using drush.
🇮🇳India Jegan2668 Bangalore
Configure your Search page/block form ID/class in the configuration field "Search FORM selectors" under /admin/config/search/search-api-tracking-settings