docs: add troubleshooting for middlewares (medusajs#13764)

Author: shahednasser

www/apps/book/app/learn/customization/custom-features/api-route/page.mdx

@@ -218,6 +218,12 @@ This returns the created brand in the response:
 }
 ```
 
+### Troubleshooting
+
+#### Returned Empty Array
+
+If you sent a request to the API route and received an empty array in the response, make sure you've correctly created the middleware at `src/api/middlewares.ts` (with correct spelling). This is a common mistake that can lead to the middleware not being applied, resulting in unexpected behavior.
+
 ---
 
 ## Summary

www/apps/book/app/learn/fundamentals/api-routes/middlewares/page.mdx

@@ -167,6 +167,10 @@ npm run dev
 Received a request!
 ```
 
+### Troubleshooting
+
+If the middleware didn't run, make sure you've correctly created the middleware at `src/api/middlewares.ts` (with correct spelling). This is a common mistake that can lead to the middleware not being applied, resulting in unexpected behavior.
+
 ---
 
 ## When to Use Middlewares

www/apps/book/generated/edit-dates.mjs

@@ -46,7 +46,7 @@ export const generatedEditDates = {
   "app/learn/fundamentals/admin/tips/page.mdx": "2025-10-03T08:35:15.022Z",
   "app/learn/fundamentals/api-routes/cors/page.mdx": "2025-03-11T08:54:26.281Z",
   "app/learn/fundamentals/admin/ui-routes/page.mdx": "2025-07-25T06:58:26.149Z",
-  "app/learn/fundamentals/api-routes/middlewares/page.mdx": "2025-07-18T15:20:25.735Z",
+  "app/learn/fundamentals/api-routes/middlewares/page.mdx": "2025-10-16T11:23:37.787Z",
   "app/learn/fundamentals/modules/isolation/page.mdx": "2025-05-21T15:10:15.499Z",
   "app/learn/fundamentals/data-models/index/page.mdx": "2025-03-18T07:59:07.798Z",
   "app/learn/fundamentals/custom-cli-scripts/page.mdx": "2025-07-25T15:32:47.587Z",
@@ -72,7 +72,7 @@ export const generatedEditDates = {
   "app/learn/debugging-and-testing/instrumentation/page.mdx": "2025-06-16T10:40:52.922Z",
   "app/learn/fundamentals/api-routes/additional-data/page.mdx": "2025-04-17T08:50:17.036Z",
   "app/learn/fundamentals/workflows/variable-manipulation/page.mdx": "2025-04-24T13:14:43.967Z",
-  "app/learn/customization/custom-features/api-route/page.mdx": "2024-12-09T10:39:30.046Z",
+  "app/learn/customization/custom-features/api-route/page.mdx": "2025-10-16T11:23:11.195Z",
   "app/learn/customization/custom-features/module/page.mdx": "2025-05-06T16:10:50.090Z",
   "app/learn/customization/custom-features/workflow/page.mdx": "2024-12-09T14:36:29.482Z",
   "app/learn/customization/extend-features/extend-create-product/page.mdx": "2025-01-06T11:18:58.250Z",

www/apps/book/public/llms-full.txt

@@ -1384,6 +1384,12 @@ This returns the created brand in the response:
 }
 ```
 
+### Troubleshooting
+
+#### Returned Empty Array
+
+If you sent a request to the API route and received an empty array in the response, make sure you've correctly created the middleware at `src/api/middlewares.ts` (with correct spelling). This is a common mistake that can lead to the middleware not being applied, resulting in unexpected behavior.
+
 ***
 
 ## Summary
@@ -8180,6 +8186,10 @@ npm run dev
 Received a request!
 ```
 
+### Troubleshooting
+
+If the middleware didn't run, make sure you've correctly created the middleware at `src/api/middlewares.ts` (with correct spelling). This is a common mistake that can lead to the middleware not being applied, resulting in unexpected behavior.
+
 ***
 
 ## When to Use Middlewares