How to retrieve recurring appointment slots using Calendar API

I’m trying to work with recurring appointment slots that I created in my calendar. These are the booking schedules that repeat automatically, not regular events.

I’ve been struggling to fetch these appointment schedules through the API. I tried using both events().list() and events().instances() methods but neither seems to return the appointment schedules I created.

Here’s my current Python implementation:

from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
import datetime
import os

def fetch_appointments():
    # Authentication setup
    credentials = Credentials.from_authorized_user_file('auth.json', ['https://www.googleapis.com/auth/calendar'])
    calendar_service = build('calendar', 'v3', credentials=credentials)
    
    # Time range setup
    start_time = datetime.datetime.utcnow().isoformat() + 'Z'
    end_time = (datetime.datetime.utcnow() + datetime.timedelta(days=14)).isoformat() + 'Z'
    
    # Attempt to get recurring instances
    response = calendar_service.events().instances(
        calendarId='primary',
        eventId='my_recurring_event_id',
        timeMin=start_time,
        timeMax=end_time,
        maxResults=50
    ).execute()
    
    appointment_slots = response.get('items', [])
    
    if not appointment_slots:
        print('No appointment slots found')
        return
    
    for slot in appointment_slots:
        slot_time = slot['start'].get('dateTime', slot['start'].get('date'))
        print(f'{slot_time}: {slot["summary"]}')

fetch_appointments()

The code runs without errors but always returns empty results. What’s the correct way to access these recurring appointment schedules through the Google Calendar API?