The panel needs a plugin or integration
Gameplay panels draw from game events and plugin integrations (for example an economy or votes plugin). If none reports, the panel is empty and says what is missing. Settings, Data sources shows which plugins are detected for each data channel with their counts for the last 24 hours.
The range is longer than your plan
Queries are clamped to your plan's history (Free 24 hours, Operator 90 days, Network 2 years). A clamped chart says so. After a downgrade, older data is hidden for 30 days before it is deleted (details).
Free plan buckets
On Free the finest bucket is 5 minutes; Operator and Network get 1 minute, and Network can view 10-second detail for the last 6 hours.
Days start at the wrong time
Days and weeks follow your organisation's timezone (UTC by default), not the browser's. Set it in Settings, General. Rollups and stored timestamps stay in UTC.
Players online above the slots
If an agent reports more players than the server's slot count, the data is kept as measured and the agent is warned that its slot count or player count is wrong.
Retention or churn shows nothing
Retention needs Operator or Network, and a day-N rate only counts players old enough to have had N days.
A metric is simply not available for your game
Not every game reports every metric: Folia has no per-tick lag spikes, basic mode has no lag data, and some games are read-only. The game's page under Games lists what is tracked.