I am missing 6 months of transaction that should be linked

Let's get your six months missing transactions back in QuickBooks, @keithcampbell-sc.

I want to ensure your missing transactions will get back in your QuickBooks Online account without a moment's delay. Thus, you can categorize and reconcile your account. 

If your bank is new in our online banking feature, note that some banks let you download the last 90 days of transactions (count start in the first connection). Others can go back as far as 24 months. Check this out for more information: Connect bank and credit card accounts to QBO.

If it's not new, I'd recommend manually updating the connection. To do this, follow the steps below: 

1. Go to the Banking tab on the upper left pane. 
2. Click the Update button. 
3. Repeat the steps until you'll see the missing transactions.

For more details, visit this link: What to do if you can’t find downloaded transactions in QuickBooks Online.

If the issue persists, I'd suggest importing the bank transactions manually as a workaround. This way, you can categorize and reconcile the account regularly. 

Proceed as follows:

1. Sign in to your bank website and follow the instructions to download your transactions as a comma-separated value (CSV) file.
2. Go to the Banking tab on the left side.
3. Click the Link account drop-down and choose Upload from file.
4. Tap Browse and pick the data.

       5. Review all the fields, then tap Next.

       6. Click Let's go to complete the process.

For more information, check out this article: Manually upload transactions in QuickBooks.

Further, check out these articles below on how to troubleshoot import and reconciliation errors in QuickBooks: 

• Fix bank upload errors in QuickBooks Online
• Fix issues for accounts you've reconciled in the past in QuickBooks Online

Lastly, may I know what is your bank's name? This way, I can check our reports to see if there are problems reported. Doing this will help me provide the most appropriate troubleshooting steps to help resolve the issue. 

Drop a line if you have follow-up questions about your bank feeds. I'm happy to answer all of your questions. Keep safe, keithcampbell-sc.

@keithcampbell-sc 

Another option, utilize MT Online as a workaround. It is designed to import into any bank or credit card in QuickBooks Online, so there is no specific setting needed. 

https://www.moneythumb.com/?ref=110