If you've already set up Dynamic Re-Ranking, but you're not seeing any impacts or getting "Low Re-Ranking Effect" and/or "Click & Conversion" warning in the Re-Ranking tab, it's possibly because:
1. Your Analytics is not getting enough search traffic
2. You are not getting enough click and conversion events on a record for a given query
Please note that it re-ranks per query. You need at least 20 clicks or 2 conversion events during the last 30 days on a record for a given query for the record to be eligible for re-ranking for that query.