How to fix - Update plannertaskdetails - If-Match header contains an invalid value - postman

Question

I am trying to update (PATCH) an existing Microsoft Planner task, to add one (1) checklist item to it. I am using Microsoft doc https://learn.microsoft.com/en-us/graph/api/plannertaskdetails-update?view=graph-rest-1.0&tabs=javascript as a reference, and I am using Postman to send the request.
{
"error": {
"code": "",
"message": "The If-Match header contains an invalid value.",
"innerError": {
"request-id": "7b50a25b-7c5a-443b-9a41-1b6314be4014",
"date": "2019-05-16T23:59:03"
}
}
}
As far as I can see, the If-Match key is built up exactly the same as how Microsoft's article used it.
I have found a somewhat similar article (https://powerusers.microsoft.com/t5/Connecting-To-Data/Custom-Connector-Graph-The-If-Match-header-must-be-specified-for/td-p/144092), but this person is filling in the If-Match value differently, and it doesn't work for me at all...
I reused the eTAG value from the response received after creating the task in the first place:
"#odata.etag": "W/\"JzEtVGFzayAgQEBAQEBAQEBAQEBAQEBARCc=\""
Does anyone have a clue what I am doing wrong here?
This is my PATCH:
https://graph.microsoft.com/v1.0/planner/tasks/n...................pYAM-DX/details
These are my headers:
Content-Type: application/json
Authorization: Bearer eyJ0eXAiOiJKV1QiLCJub..........
If-Match: W/"JzEtVGFzayAgQEBAQEBAQEBAQEBAQEBARCc="
This is my body:
{
"previewType": "checklist",
"checklist": {
"{{$guid}}":{
"#odata.type": "microsoft.graph.plannerChecklistItem",
"title": "Update task details",
"isChecked": false
}
}
}
I was expecting the If-Match key to be correct, as I have used the Microsoft article, but somehow it results in the error message:
"The If-Match header contains an invalid value."

Answer 1

I had similar problem. I used etag from task when updates Task details.
The Task and Task Details are different objects.
Check on - MS Graph doc
Get etag value from Task details of created task using:
GET https://graph.microsoft.com/v1.0/planner/tasks/{task-id}/details