NodeJS: aws-sdk sts.assumeRole is not working

I have a weird problem where I can't seem to go anywhere with. I have followed everything online (multiple tutorials etc) but can't get sts.assumeRole to work.

My set-up:

• Main AWS account (used for billing, IAM etc)
• Sub AWS account 1 (used for customer 1)
• Sub AWS account 2 (used for customer 2)
• etc

I have a bot running in Sub AWS account 1 where I need pricing information from the Main AWS account.

So, I created a role on the Main AWS account to have AWS ce:* access, below:

{
    "Version": "2012-10-17",
    "Statement": [{
            "Effect": "Allow",
            "Action": ["ce:*"],
            "Resource": ["*"]
        }]
}

Trust Relationship

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "ec2.amazonaws.com",
        "AWS": "arn:aws:iam::SubAWSaccount1-ID:role/instance-profile"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

Now, this is the instance-profile attached to the EC2 instance running on the Sub AWS account 1:

"Version": "2012-10-17",
"Statement": [
    {
        "Sid": "VisualEditor1",
        "Effect": "Allow",
        "Action": "sts:AssumeRole",
        "Resource": "arn:aws:iam::mainAWSaccount-ID:role/botRole"
    }
  ]
}

Trust relationship

{
  "Version": "2012-10-17",
  "Statement": [
   {
    "Sid": "",
    "Effect": "Allow",
    "Principal": {
      "Service": "ec2.amazonaws.com"
    },
    "Action": "sts:AssumeRole"
   }
  ]
}

Okay, that being out of the way, this is the code that is not working:

var AWS = require('aws-sdk');
var pricingAWS = new AWS.CostExplorer();

var getPricing = function(){

    var costParams = {
        TimePeriod: { Start: "2019-12-01 ", End: "2020-01-01"},
        Granularity: 'MONTHLY',
        Metrics: ['BlendedCost'],
        Filter: {      
            Dimensions: {
                Key: "LINKED_ACCOUNT",
                Values: ["Sub AWS account 2s ID"] //Main AWS account has access to many sub accounts info. So bot in running on Sub account 1, I need info from Sub account 1, 2, 3 etc and Role is on Main account
            }
        }
    };

    var roleToAssume = {
        RoleArn: 'arn:aws:iam::mainAWSaccount-ID:role/botRole',
        RoleSessionName: 'testTestTest',
        DurationSeconds: 900
    };

    var roleCreds = {};

    sts.assumeRole(roleToAssume, function(err, data) {
        if (err) {
            console.log(err);
        } else {
            roleCreds = {
                accessKeyId: data.Credentials.AccessKeyId,
                secretAccessKey: data.Credentials.SecretAccessKey,
                sessionToken: data.Credentials.SessionToken
            };

            pricingAWS.config.update({
                accessKeyId: roleCreds.AccessKeyId,
                secretAccessKey: roleCreds.SecretAccessKey,
                sessionToken: roleCreds.SessionToken
              });
        }
    });

    pricingAWS.getCostAndUsage(costParams, function (err, data) {
        if (err) {
            reject(err);
        }else{
            resolve(data);
        }
    });
};

getPricing();

What I get from the console.log(err)is:

User: arn:aws:sts::SubAWSAccount-1:assumed-role/slack-instance-profile/instanceID is not authorized to perform: ce:GetCostAndUsage on resource: arn:aws:ce:us-east-1:SubAWSAccount-1:/GetCostAndUsage'