# Why Is No Explorer Data Loading?

If the explorer at **https://explorer.d-bis.org** shows no stats, no blocks, and no transactions (or only "—" and "Loading..."), the **Explorer API backend is not responding**.

## Root cause

- The frontend loads all data from **`/api/`** (e.g. `/api/v2/stats`, `/api/v2/blocks`, `/api/v2/transactions`).
- Nginx proxies **`/api/`** to **Blockscout** on **port 4000** (`http://127.0.0.1:4000`).
- When Blockscout is not running or not reachable, nginx returns **502 Bad Gateway** (sometimes 503).
- Every API request then fails, so **no info loads**.

## How to fix it

1. **On the Proxmox host** that runs the explorer VM (VMID 5000):
   ```bash
   cd /path/to/explorer-monorepo
   bash scripts/fix-502-blockscout.sh
   ```
   Or from your machine if the script supports SSH:
   ```bash
   EXPLORER_VM_HOST=root@192.168.11.12 bash scripts/fix-502-blockscout.sh
   ```

2. **Manually** (inside the explorer VM, VMID 5000):
   - Start PostgreSQL if used: `docker start blockscout-postgres`
   - Start Blockscout: `cd /opt/blockscout && docker compose up -d`
   - Ensure the Blockscout container is listening on **port 4000**.

3. **Verify** the API is up:
   ```bash
   curl -sS -o /dev/null -w "%{http_code}" https://explorer.d-bis.org/api/v2/stats
   ```
   You should see `200`. If you see `502`, the backend is still down.

## More detail

- **502** = nginx is up but the upstream (Blockscout on port 4000) is down or unreachable.
- Full runbook: [EXPLORER_API_ACCESS.md](./EXPLORER_API_ACCESS.md) (Fix 502, Blockscout, nginx proxy).
- API reference: [EXPLORER_API_REFERENCE.md](./EXPLORER_API_REFERENCE.md).