1. Search working based on the indexing file. Your search string not available in the index file, its never give a result. Next we will use for old: option. Its will search in DB. You will get a result from DB.
2. Go to System>Settings>Search Landing page and Select All Rule, All Data and Complete the re-index. Once indexing done, No need to use Old.
Starting in Pega 7.1.7, the full-text search engine changed from Lucene search to Elasticsearch.
Compared to Lucene search, where index files are stored and accessed on a single node, Elasticsearch is architected from the ground up for use in distributed environments, and automatically provides a more robust, fault-tolerant search capability. Additionally, Elasticsearch can detect and remove failed nodes in a cluster, and automatically replicates and reorganizes nodes as needed.