I have all the information on how to get those missing transactions into QuickBooks Online, usercolarussop.
When you link your bank account to QuickBooks Online, it will automatically download transactions from the last 90 days, and in some banks, it can even import data as far back as 24 months. However, if you need to show all transactions from a period beyond the initial download, you can follow these steps:
Log in to your bank or credit card's website.
Follow the instructions provided by your bank to download CSV files containing your transaction history to your computer. Every financial institution has different steps.
Make sure the date range for the download is at least one day before your oldest transaction.
Download the transactions and save the file in a location that is easily accessible, such as your computer's desktop.
Then, upload the transactions to QBO. You can follow the steps below.
Go to Banking and select Banking.
Select the blue tile for the account.
Click the Link account dropdown and then Upload from file.
Pick Drag and drop or select files and select the file you downloaded from your bank. Then select Continue.
In the QuickBooksaccount dropdown, select the account you want to upload. Then click Continue.
Follow the onscreen steps to match the columns on the file with the correct fields in QuickBooks. Then select Continue.
Choose the transactions you would like to import. Then hit Continue.