Add row to SharePoint List (People or group column multiple ID's) in Rest API

Question

I'm trying to add multiple people into a list column of the type People or Group that can have more than 1 person.

My Column ProjectOwner doesn't exist If I pick up the data in the rest API, but there are 2 columns (ProjectOwnerStringId and ProjectOwnerId). Whatever I try I get the error:

"Internal error in microsoft_sharepoint. (ID: a043fdc8-ee96-4cb9-9f0c-2bf6ab6756c7) Internal error".

Any help would be welcome

data:

{
      ProjectOwnerId: 
[
         15,
         29
      ],
      SPO_OwnerId: 15,
      ProjectName: test3,
      ProjectStartDate: 2022-10-15T13:35:20.000000+00:00,
      ProjectEndDate: 2199-12-31T00:00:00.000000+00:00,
      Project_Template: Ireland,15953,
      ProjectCurrency: 0.0,
      ProjectLocation: Please enter the project location,
      ProjectCode_CDE: BC1234,
      ProjectTimezone: Europe/London,
      JobNumber: Please enter the Job Number,
      ProjectType: Data Center,
      GoToURL: Complete,
      B360_Status: Complete,
      ProjectOwnerStringId: 
[
         15,
         29
      ],
      SPO_OwnerStringId: 15
    }
  },
  request_headers: 
[
     
{
      name: accept,
      value: application/json;odata=verbose
    },
     
{
      name: Content-Type,
      value: pplication/json
    },
     
{
      name: If-Match,
      value: *
    },
     
{
      name: X-HTTP-Method,
      value: MERGE
    }
  ],
  Action name: Add row toSites list,
  Method: post
}

Answer 1

As your ProjectOwner column is multiple selection person or group column, you have to pass the array of user IDs to ProjectOwnerId property like:

ProjectOwnerId: { 'results': [15, 29] }

Reference: Update People picker column using REST API in Power Automate

---

Additional information:

For single selection person of group field, you can directly pass the user ID like:

ProjectOwnerId: 15