There are a few reasons a dashboard can read zero. Work through these in order.
1. Timezone mismatch — the most common cause
Your dashboard reports in the timezone set on your profile. If that doesn't match where you're looking from, "today" may not have started yet. Set your correct local timezone in profile settings and the numbers will line up.
2. Date range
Widen the selected period. A card with no data in the chosen range shows zero even when the campaign is delivering fine.
3. The campaign genuinely isn't delivering
If the numbers are still zero over a wide range, it's not a reporting issue. Run Campaign Health Check on the campaign — it checks bid, budget, balance, creatives, targeting breadth and whether the Insertion Order has expired, and usually names the cause in one step.
See also: Why isn't my campaign getting any traffic?
4. Conversions specifically showing zero
Impressions and clicks fine, conversions at zero usually means the postback isn't wired up. Check your tracking URL carries {CLICK_ID} and that your tracker is firing back — see Supported Macros.