// Force flush rewrite rules for Rank Math sitemaps
add_action('init', function() {
    if (!get_option('rankmath_sitemap_flushed')) {
        flush_rewrite_rules();
        update_option('rankmath_sitemap_flushed', true);
    }
});
```

Click **Update File** then visit `techsyntro.com/sitemap_index.xml` — should work now.

---

**If that doesn't work — Step 2:**

The fastest fix without touching code:
```
WordPress Admin → Settings → Permalinks
→ Change to "Plain" → Save
→ Change back to "Post name" → Save
```

This force-flushes all rewrite rules.

---

**If still 404 — Step 3 (nuclear option):**
```
WordPress Admin → Plugins → Add New
→ Search: "Rank Math Sitemap Fixer" or "XML Sitemap"
→ Or deactivate ALL plugins except Rank Math temporarily
→ Test sitemap URL
→ Re-activate plugins one by one
```

This identifies which plugin is conflicting with Rank Math's sitemap rewrite rules.

---

**While you're fixing this — update your robots.txt too.**

Right now it points to the broken URL. Change it to the working one:
```
WordPress Admin → Rank Math SEO → General Settings → Edit robots.txt
```

Change:
```
Sitemap: https://techsyntro.com/sitemap_index.xml
```
To:
```
Sitemap: https://techsyntro.com/?sitemap=1