diff --git a/app/agenda/page.tsx b/app/agenda/page.tsx
index 63fcdcd..a55f58c 100644
--- a/app/agenda/page.tsx
+++ b/app/agenda/page.tsx
@@ -146,12 +146,51 @@ export default async function CalendarPage() {
       }
     });
 
-    // If sync exists but is disabled, re-enable it instead of creating a new calendar
+    // If sync exists but is disabled, check if it's due to invalid credentials
+    // Don't re-enable if the last error was 401 (invalid credentials)
     if (existingSync && !existingSync.syncEnabled) {
-      await prisma.calendarSync.update({
-        where: { id: existingSync.id },
-        data: { syncEnabled: true }
-      });
+      const isAuthError = existingSync.lastSyncError?.includes('401') || 
+                          existingSync.lastSyncError?.includes('Unauthorized') ||
+                          existingSync.lastSyncError?.includes('invalid');
+      
+      if (!isAuthError) {
+        // Only re-enable if it's not an authentication error
+        await prisma.calendarSync.update({
+          where: { id: existingSync.id },
+          data: { syncEnabled: true }
+        });
+      } else {
+        // Try to discover calendars to verify if credentials are now valid
+        try {
+          const { discoverInfomaniakCalendars } = await import('@/lib/services/caldav-sync');
+          const externalCalendars = await discoverInfomaniakCalendars(
+            account.email,
+            account.password!
+          );
+          
+          if (externalCalendars.length > 0) {
+            // Credentials are now valid, re-enable sync
+            await prisma.calendarSync.update({
+              where: { id: existingSync.id },
+              data: { 
+                syncEnabled: true,
+                lastSyncError: null,
+                externalCalendarId: externalCalendars[0].id,
+                externalCalendarUrl: externalCalendars[0].url
+              }
+            });
+          }
+        } catch (error) {
+          // Credentials are still invalid, keep sync disabled
+          const errorMessage = error instanceof Error ? error.message : 'Unknown error';
+          await prisma.calendarSync.update({
+            where: { id: existingSync.id },
+            data: {
+              lastSyncError: `Identifiants invalides ou expirés (${errorMessage}). Veuillez vérifier vos identifiants Infomaniak dans la page courrier.`
+            }
+          });
+        }
+      }
       continue; // Skip to next account
     }
 
@@ -211,7 +250,30 @@ export default async function CalendarPage() {
         }
       } catch (error) {
         // Log error but don't fail the page - account may not have calendar access or credentials may be invalid
-        console.log(`Infomaniak calendar sync not available for ${account.email} - ${error instanceof Error ? error.message : 'Unknown error'}`);
+        const errorMessage = error instanceof Error ? error.message : 'Unknown error';
+        console.log(`Infomaniak calendar sync not available for ${account.email} - ${errorMessage}`);
+        
+        // If it's a 401 error, the credentials are likely invalid - update lastSyncError in existing sync if any
+        if (errorMessage.includes('401') || errorMessage.includes('Unauthorized')) {
+          // Check if there's a disabled sync for this account
+          const disabledSync = await prisma.calendarSync.findFirst({
+            where: {
+              mailCredentialId: account.id,
+              provider: 'infomaniak',
+              syncEnabled: false
+            }
+          });
+          
+          if (disabledSync) {
+            // Update the error message
+            await prisma.calendarSync.update({
+              where: { id: disabledSync.id },
+              data: {
+                lastSyncError: `Identifiants invalides ou expirés (401 Unauthorized). Veuillez vérifier vos identifiants Infomaniak dans la page courrier.`
+              }
+            });
+          }
+        }
         // Continue with other accounts even if one fails
       }
     }
@@ -423,9 +485,13 @@ export default async function CalendarPage() {
     const hasActiveSync = cal.syncConfig?.syncEnabled === true && cal.syncConfig?.mailCredential;
     
     // Exclude "Privée"/"Default" calendars that are not actively synced
-    // Also log for debugging if Infomaniak calendar is missing
-    if (isPrivateOrDefault && cal.syncConfig?.provider === 'infomaniak' && !hasActiveSync) {
-      console.log(`Infomaniak calendar found but sync is disabled: ${cal.id}, syncEnabled: ${cal.syncConfig?.syncEnabled}`);
+    // Log for debugging if Infomaniak calendar is missing
+    if (isPrivateOrDefault && cal.syncConfig?.provider === 'infomaniak') {
+      if (!hasActiveSync) {
+        console.log(`Infomaniak calendar found but sync is disabled: ${cal.id}, syncEnabled: ${cal.syncConfig?.syncEnabled}, error: ${cal.syncConfig?.lastSyncError || 'none'}`);
+      } else {
+        console.log(`Infomaniak calendar is active: ${cal.id}, email: ${cal.syncConfig?.mailCredential?.email}`);
+      }
     }
     
     if (isPrivateOrDefault && !hasActiveSync) {