Why is my GA4 custom exploration missing data after 2 months?.

This is the number one most common complaint with Google Analytics 4. You go to build a custom Funnel Exploration or Path Analysis for Q4 of last year, and the report turns up entirely blank, even though the standard overview reports show traffic.

Google did this for privacy compliance (GDPR), but it severely limits analysis out-of-the-box. Your standard reports use aggregated, anonymized tables, which is why they still work, but Explorations rely on user-level data, which expires in 60 days unless changed.