I need to reactivate my account to send customer invoices

We'd love to have you back, graham. 

I'm happy to help you reactivate your QuickBooks Online (QBO) account. Here's a step-by-step guide on how to do it:

1. Sign in to your QuickBooks Online company.
2. Go to Settings and select Subscriptions and billing.
3. Select Resubscribe and choose the New payment method (Credit/Debit Card or PayPal).
4. Enter the updated payment and billing information and hit Resubscribe.

Next, you'll have to sign out and in again to make sure your QuickBooks Online account is updated.

1. Sign out, then sign in again.
2. Go to Settings and select Subscriptions and billing.
3. Check the Next charge date. If it's a date in the past, contact support to prevent back-billed charges from occurring.

In addition, you may find this article helpful, which contains answers to some frequently asked questions regarding resubscribing or reactivating to QBO: Resubscribe to or reactivate QuickBooks Online

Once you've resubscribed to QuickBooks, you can proceed with creating invoices and sending them to your customers. 

Feel free to return at any time if you have any further questions about resubscribing to QBO. I'm here to assist you. Take care and best of luck!