-check proxy configurations, as mentioned in article - If you are using Search&Promote with a custom proxy configuration, you need to configure both HTTP Client proxy configurations as some functionalities of AEM are using the 3.x APIs and some others the 4.x APIs
- create a debug logger on 'com.day.cq.searchpromote' and look out for errors/warnings
-validate that the page root is configured with SnP configuration as mentioned in that article - Configure web pages so that they use a specific Search&Promote service. Search&Promote components automatically use the service of their host page.
Based on your AEM version, check if there is any hotfix/package to be installed before you proceed further.