Let's make sure to bring the missing bank transactions to QuickBooks Online.
Just to confirm, is this your first time to link an account to QuickBooks? If so, QuickBooks Online automatically downloads the last 90 days of transactions. If the missing ones are more than 90 days transactions, you can export additional historical transactions from the bank and upload them into your QuickBooks company.
First, download transactions from your bank by logging in to your bank's website. Then, follow the given instructions on how to download transactions and save the file on your desktop or anywhere you can easily find it.
Once done, upload them to your book by following these steps:
Sign to your QBO account and select Transactions on the left panel.
Click the Link account drop-down arrow.
Select Upload from file. Then, click the file you've saved on your computer.
On the other hand, we can update your bank account manually to get the most current view of your data. Go to Transactions and select the Banking tab > select Update. If you've tried this procedure already, I'd suggest logging in to your bank website to check if there's an ongoing issue in your bank.
You can use these articles as additional reference about categorizing transactions and reconciliation workflow in QBO:
You can also share with me the name of your bank. This way, I can check more resources and provide accurate details about your concern. Please visit again if you need more assistance. Take care always, usercaznacleaningsol.