Cloud SQL instance not being stopped using Cloud Scheduler

Cloud SQL instance is not being stopped using Cloud Schedule after these steps:

1. Create a pub/sub topic that is supposed to trigger the cloud function.
2. Deploy a cloud function using the topic already created in step 1, with the below python (3.8) code file and requirements. (Entry point: start_stop)
3. Create a cloud scheduler job to trigger the cloud function on a regular basis with the topic created in step 1. The payload is set to start [CloudSQL instance name] or stop [CloudSQL instance name] to start or stop the specified instance

Main.py:

from googleapiclient import discovery
from oauth2client.client import GoogleCredentials
import base64
from pprint import pprint

credentials = GoogleCredentials.get_application_default()
service = discovery.build('sqladmin', 'v1beta4', credentials=credentials, cache_discovery=False)
project = 'projectID'

def start_stop(event, context):
  print(event)
  pubsub_message = base64.b64decode(event['data']).decode('utf-8')
  print(pubsub_message)
  command, instance_name = pubsub_message.split(' ', 1)

  if command == 'start':
    start(instance_name)
  elif command == 'stop':
    stop(instance_name)
  else:
    print("unknown command " + command)

def start(instance_name):
  print("starting " + instance_name)
  patch(instance_name, "ALWAYS")

def stop(instance_name):
  print("stopping " + instance_name)
  patch(instance_name, "NEVER")

def patch(instance, activation_policy):
  request = service.instances().get(project=project, instance=instance)
  response = request.execute()
  j = response["settings"]
  settingsVersion = int(j["settingsVersion"])
  
  dbinstancebody = {
    "settings": {
      "settingsVersion": settingsVersion,
      "activationPolicy": activation_policy
    }
  }

  dbinstancebody = {
    "settings": {
      "settingsVersion": response["settings"]["settingsVersion"],
      "activationPolicy": activation_policy
    }
  }

  request = service.instances().update(
    project=project,
    instance=instance,
    body=dbinstancebody)
    
  response = request.execute()
  pprint(response)

Requirements.txt

google-api-python-client==1.10.0
google-auth-httplib2==0.0.4
google-auth==1.21.1
oauth2client==4.1.3

When I click RUN NOW button in the stop scheduler, it's executed successfully, but when I navigate to SQL instance, it is not stopped. Can someone spot what I am missing? If you need more details, just let me know please, I have just started with GCP. :)