diff --git a/api/dropbox-proxy.js b/api/dropbox-proxy.js
index 6e3deea..b44ea56 100644
--- a/api/dropbox-proxy.js
+++ b/api/dropbox-proxy.js
@@ -42,14 +42,21 @@ export default async function handler(req, res) {
   }
 
   try {
-    const sharingUrl = 'https://www.dropbox.com/scl/fi/ulcgt5iyyvrkeynprhali/Data-Matrix.xlsx?rlkey=i9p9xgwzm0fr7jip91vxdeal5&st=k8jmibh4&dl=1';
+    const sharingUrl = 'https://www.dropbox.com/scl/fi/8qbl7uoigtfu5x1nn8wvm/Data-Matrix.xlsx?rlkey=s6rkwa2bjrx9gh442gw6w40uk&dl=1';
     const upstream = await fetch(sharingUrl, {
       method: 'GET',
       headers: {
-        'Cache-Control': 'no-cache'
+        'Cache-Control': 'no-cache',
+        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36'
       }
     });
 
+    const contentType = upstream.headers.get('content-type');
+    if (contentType && contentType.includes('text/html')) {
+      console.error('Dropbox returned HTML instead of file');
+      return res.status(500).send('Error: El enlace de Dropbox ha devuelto una página HTML en lugar del archivo. Es probable que el enlace haya caducado o necesite ser renovado.');
+    }
+
     if (!upstream.ok) {
       const errText = await upstream.text();
       console.error('Dropbox URL error:', upstream.status, errText);
diff --git a/src/App.tsx b/src/App.tsx
index 2d84c14..dee265d 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -61,10 +61,15 @@ export default function App() {
         
         if (isDev) {
           const cacheBuster = `t_${Date.now()}`;
-          const fileUrl = `/dropbox-file/scl/fi/ulcgt5iyyvrkeynprhali/Data-Matrix.xlsx?rlkey=i9p9xgwzm0fr7jip91vxdeal5&st=k8jmibh4&dl=1&${cacheBuster}=${Date.now()}`;
+          const fileUrl = `/dropbox-file/scl/fi/8qbl7uoigtfu5x1nn8wvm/Data-Matrix.xlsx?rlkey=s6rkwa2bjrx9gh442gw6w40uk&dl=1&${cacheBuster}=${Date.now()}`;
           console.log('Fetching Data-Matrix.xlsx from Dropbox (hard refresh)...');
           const response = await fetch(fileUrl, { cache: 'no-store' });
           if (!response.ok) throw new Error(`HTTP ${response.status}`);
+          
+          const contentType = response.headers.get('content-type');
+          if (contentType && contentType.includes('text/html')) {
+            throw new Error('Dropbox returned an HTML page instead of the Excel file. This usually means the sharing link has expired or requires manual interaction. Please generate a new "Copy Link" from Dropbox.');
+          }
           const arrayBuffer = await response.arrayBuffer();
           if (arrayBuffer.byteLength < 100) throw new Error('File too small');