Make sure you've updated your payment information to activate your QuickBooks Online subscription. Let me guide you how to update your payment information.
To change or update your payment details
Click on the Gear icon, then choose Account and Settings.
Click on the Billing & Subscription tab.
Under Payment method, select Edit.
Enter the full credit card information by typing in the complete card number, name on the card, expiration date, and security code.
Verify that the billing address in QuickBooks Online is the same on your credit card statement.
Click Save Changes.
Once done, the system will attempt to process the billing to your account within 24 hours. Once successful the account should be reinstated and ready for use.
If the issue persists, I'd recommend contacting our Customer Care Team. That way one of our supports can ask for your details and check your subscription status.