The last few months of last year's, and the first six month's of this year's transactions are not showing from linked bank account. Do I need to manually enter these?

Welcome to the Community, @chesterwpeden. I understand how you want to get all your bank transactions to QuickBooks. 

When you first connect your bank and credit card accounts in QuickBooks, the system will only download bank transactions for the past 90 days. 

Should you need those older than 90 days transactions, you'll need to manually upload them into QuickBooks Online. 

Here's how:

1. Sign in to your bank or credit card's website, then follow your bank's instructions on downloading CSV files of your transactions. Every financial institution has different steps. Here are steps for Bank of America, Chase, and Wells Fargo.
2. Check the date range for the download. To avoid duplicates, ensure to get at least one day before the date of your oldest transaction.
3. Download your transaction and save the file somewhere you can easily find it, like your computer's desktop.

Once done, check and ensure it's in the correct format before you upload it. Then, follow the steps to upload under For accounts connected to online banking outlined in the Step 4: Manually upload the transactions.

Here's an article you can bookmark as reference when it's time for you to balance your books: Learn the reconcile workflow in QuickBooks.

I'll be with you again should you need further guidance in uploading your bank transactions. Take care!