I am unable to subscribe for 1 year

As far as I know, they don't offer the new annual subscription for the time being.

https://quickbooks.grsm.io/India

but how to renew my active subscription ... as it is showing it will expire on 9/01/2021 

I can provide some information with the process of renewing your QuickBooks Online (QBO) subscription, @consultgreentree.

You can renew your QuickBooks Online subscription by going to the Your account page on or after the expiration date.

Here's how: 

1. Click the Gear icon, then choose Subscriptions and billing.
2. Under Account activities, click Subscribe or Renew. 
3. Follow the prompts to renew your subscription.

Here's an article about subscription renewal: Renew my account subscription.

In case you'd encounter any errors, you can check the following article on how to fix “my subscription payment failed” issues. 

I'll be glad to help you with any other concerns you have with your QBO subscription. Tag me in your comments below, and I'll get back to you. Have a great rest of the day!