On of my accounts has suddenly disconnected and will not connect, what do I need to do?

Happy to guide you on what to do in your disconnected bank account, @rogersonstaff. You're in the right place for answers.
 

I'll make sure your bank account goes back to QuickBooks Online (QBO). This way, you can categorize the transactions whenever you're ready. 

Before we proceed, may I know what's your bank's name? And did you receive any error messages? Any additional information will help me provide an accurate explanation and troubleshooting steps to fix the concern without a moment's delay. 

In the meantime, I'd recommend reconnecting the bank account by following the steps below: 

1. Go to the Banking tab and select Link account. 
2. Type your bank's name in the search box and enter your credential. 
3. Follow the on-screen instructions. 

For additional details, visit this link: Connect bank and credit card accounts to QuickBooks.

If you happen to encounter errors, follow the links listed in the Step 4 section of this article to be guided in fixing it: What to do if you get a bank error or can't download transactions.

 Furthermore, check out the articles below on how to classify bank transactions and reconcile accounts in QuickBooks: 

• Reconcile an account in QuickBooks
• Categorize and match online bank transactions in QBO

I'll be around in case you need further assistance. Place a comment below, and I'll get back to you. Keep safe, rogersonstaff.