Thanks for reaching out to the Community, Sllopez.
 

After connecting a bank account to QuickBooks, its latest transactions from the last 90 days are automatically downloaded. This is why you'll only see a few months of history after linking your account.
 

If you need to import transactions from further back than 90 days, I'd recommend importing them manually.
 

Here's how:
 

1. In the left navigation bar, go to Accounting, then Chart of accounts.
2. Find which bank account you're working with.
3. Click its View register option.
4. Locate and write down the date of its oldest transaction. Usually, your oldest transaction will be the account's opening balance.
5. Sign in to your financial institution's website.
6. Follow their instructions for how to download CSV files of transactions.
7. Check the date range for your download. It should be at least one day before the date of your oldest transaction.
8. Download the transactions. Be sure to save your file somewhere you can easily find it, like the computer's desktop.

Next, you can review your file's format/size and begin uploading it.
 

To download recent transactions through the connection your client's set up, they can access their Banking screen, then select Update.
 

I've also included a detailed resource about working with online banking which may come in handy moving forward: Manually upload transactions
 

Please feel welcome to send a reply if there's any additional questions. Have a wonderful day!