If you see the personalization search code (see below) included on your site, but still cannot see the difference between normal search and personalized search, the personalization configuration must be set up properly before the query (
query.UsingPersonalization) can work.
query = query.UsingPersonalization(searchCriteria.PersonalizationScope)
First, you have to purchase the Personalized FIND service, which is separate from Optimizely Product Recommendations. For this you need to contact your customer service manager (CSM) or account manager to obtain the service.
After purchasing, the service desk team provides the provision, and then the Personalized FIND is enabled in the Personalization Portal, as shown below. From here, you can implement the code and test it.