Issue during step 2 of the Hands-On exercise, N8N101

n8n Academy N8N101: Essentials: Your First Workflows
1

Hello everyone,

When I try to complete step 2 of the hands-on exercise for the N8N101 course (Transform the data), I get an error at the final validation step when making the HTTP POST request to https://learn.app.n8n.cloud/webhook/course/n8n101/process-orders.

Here’s the error returned:

{
"errorMessage": "Your request is invalid or could not be processed by the service",
"errorDescription": "Your order totals are incorrect. Please ensure you are calculating the totals correctly.",
"errorDetails": {
"rawErrorMessage": [
"422 - \"{\\\"error\\\":\\\"Your order totals are incorrect. Please ensure you are calculating the totals correctly.\\\"}\""
],
"httpCode": "422"
},
"n8nDetails": {
"nodeName": "HTTP Request",
"nodeType": "n8n-nodes-base.httpRequest",
"nodeVersion": 4.4,
"itemIndex": 0,
"time": "19/06/2026 22:00:38",
"n8nVersion": "2.26.8 (Self Hosted)",
"binaryDataMode": "filesystem",
"stackTrace": [
"NodeApiError: Your request is invalid or could not be processed by the service",
"    at ExecuteContext.execute (/usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-nodes-base@file+packages+nodes-base\_@aws-sdk+credential-providers@3.808.0_asn1.js@5_8da18263ca0574b0db58d4fefd8173ce/node_modules/n8n-nodes-base/nodes/HttpRequest/V3/HttpRequestV3.node.ts:865:16)",
"    at processTicksAndRejections (node:internal/process/task_queues:104:5)",
"    at WorkflowExecute.executeNode (/usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-core@file+packages+core\_@opentelemetry+api@1.9.0\_@opentelemetry+exporter-trace-otlp_cf5896492347c4895f0373f4acc773d7/node_modules/n8n-core/src/execution-engine/workflow-execute.ts:1053:8)",
"    at WorkflowExecute.runNode (/usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-core@file+packages+core\_@opentelemetry+api@1.9.0\_@opentelemetry+exporter-trace-otlp_cf5896492347c4895f0373f4acc773d7/node_modules/n8n-core/src/execution-engine/workflow-execute.ts:1327:11)",
"    at /usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-core@file+packages+core\_@opentelemetry+api@1.9.0\_@opentelemetry+exporter-trace-otlp_cf5896492347c4895f0373f4acc773d7/node_modules/n8n-core/src/execution-engine/workflow-execute.ts:1778:27",
"    at /usr/local/lib/node_modules/n8n/node_modules/.pnpm/n8n-core@file+packages+core\_@opentelemetry+api@1.9.0\_@opentelemetry+exporter-trace-otlp_cf5896492347c4895f0373f4acc773d7/node_modules/n8n-core/src/execution-engine/workflow-execute.ts:2474:11"
]
}
}

I’ve followed the entire workflow as described in the instructions, but I keep getting the same response from the HTTP request.

Has anyone been able to validate this step?

Here’s my workflow:

Thank you for your help!

2

Hello,

This is a hardone to see. You have a space in your ’ order_total’ variable so it’s failing. Remove the space at the beginning and you’re good to go.

cheers,

3

Wow thank you so much, it works!

I’m curious to know how you found that error?

4

Our backend was throwing the invalid variable name, and when I expected the payload being sent, i noticed there was a space in the name. It took me a good 10 minutes to notice it as well.