Cloud Schedule Cloud Function to read and write data to BigQuery fails

Question

I am trying to schedule a read and write Cloud Function in GCP, but I keep getting a fail on the execution of the scheduling in Cloud Scheduler. My function (which b.t.w. is validated and activated by Cloud Functions) is given by

def geopos_test(request):
    from flatten_json import flatten
    import requests
    import flatten_json
    import pandas as pd
    import os, json, sys,glob,pathlib
    import seaborn as sns
    from scipy import stats
    import collections
    try:
        collectionsAbc = collections.abc
    except AttributeError:
      collectionsAbc = collections 
    import numpy as np
    import pandas as pd
    import matplotlib as mpl
    import matplotlib.pyplot as plt
    import matplotlib.colors as colors
    import matplotlib.ticker as ticker
    import datetime
    import seaborn as sns
    from mpl_toolkits.axes_grid1 import make_axes_locatable
    from matplotlib.colors import ListedColormap, LinearSegmentedColormap
    from matplotlib.lines import Line2D
    import numpy as np
    import math
    from pandas.io.json import json_normalize
    from operator import attrgetter
    from datetime import date, timedelta
    import pandas_gbq
    import collections
    from google.cloud import bigquery

    client = bigquery.Client()
    project = "<ProjectId>"
    dataset_id = "<DataSet>"
    dataset_ref = bigquery.DatasetReference(project, dataset_id)
    table_ref = dataset_ref.table('sectional_accuracy')
    table = client.get_table(table_ref)

    Sectional_accuracy = client.list_rows(table).to_dataframe()
  
    sectional_accuracy = sectional_accuracy.drop_duplicates()
    sectional_accuracy.sort_values(['Store'])
  
    job_config = bigquery.LoadJobConfig(
    schema=[
       
        bigquery.SchemaField("Store", bigquery.enums.SqlTypeNames.STRING),
        bigquery.SchemaField("storeid", bigquery.enums.SqlTypeNames.STRING),
        bigquery.SchemaField("storeIdstr", bigquery.enums.SqlTypeNames.STRING),
        bigquery.SchemaField("Date", bigquery.enums.SqlTypeNames.TIMESTAMP),
        bigquery.SchemaField("Sections", bigquery.enums.SqlTypeNames.STRING),
        bigquery.SchemaField("Percentage", bigquery.enums.SqlTypeNames.FLOAT),
        bigquery.SchemaField("devicePercentage", bigquery.enums.SqlTypeNames.FLOAT),
        bigquery.SchemaField("distance", bigquery.enums.SqlTypeNames.STRING),

    ],)

    NtableId = '<ProjectId>.<DataSet>.test'
    job = client.load_table_from_dataframe(sectional_accuracy, Ntable_id, job_config=job_config)
    

This function only reads data from one table and writes it to a new one. The idea is to do a load of transformations between the reading and writing.

The Function is associated to the App Engine default service account for which I am the owner and I have added (probably overkill) The Cloud Run Invoker, Cloud Functions Invoker and Cloud Scheduler Job Runner.

Now, for the Cloud Scheduler:

I have defined it by HTTP with POSTmethod with an URL, AUth OIDC token with the same service account as that used by the function. As for the HTTP header, I have User-Agent with value Google-Cloud-Scheduler. Note that I have no other header as I am uncertain of what it should be.

Yet, it fails every single time with a PERMISSION DENIED message in the log.

What Have I tried:

• Change geopos_test(request) to geopos_test(event, context)
• Tried to change the HTTP header to (Content-Type, application/octet-stream) or (Content-Type, application/json)
• Change service account

What I haven't tried is to give some value in body, since I do not know what it could be.

I am now out of ideas. Any help would be appreciated.

Update: Error message:

{
httpRequest: {1}
insertId: "********"
jsonPayload: {
@type: "type.googleapis.com/google.cloud.scheduler.logging.AttemptFinished"
jobName: "******************"
status: "PERMISSION_DENIED"
targetType: "HTTP"
url: "*************"
}
logName: "*************/logs/cloudscheduler.googleapis.com%2Fexecutions"
receiveTimestamp: "2022-10-24T10:10:52.337822391Z"
resource: {2}
severity: "ERROR"
timestamp: "2022-10-24T10:10:52.337822391Z"