Not receiving invoices in pdf format, even though it is ticked

Welcome to the Community, Jason197. 

I see that you have enabled and checked the PDF option but are still not receiving the attachment. Let's double-check the settings to ensure everything is set up correctly. Please follow the steps below:

1. Click on the Gear icon at the top.
2. Choose Accounts and Settings.
3. Go to the Sales tab.
4. Click on the pencil icon next to Online delivery.
5. Ensure that the PDF Attached box is checked.
6. Don't forget to click Save before clicking Done.

Once done, you can test by sending an invoice to your email to check if the PDF attachment is available. If the issue persists, I recommend using a private browser or incognito window to eliminate any errors or glitches that may be occurring in the system. Here are the keyboard shortcuts for different browsers:

• Google Chrome: Ctrl + Shift + N 
• Safari 11 or newer: ⌘ + Shift + N
• Mozilla Firefox: Shift + Ctrl + P
• Microsoft Edge: Ctrl + Shift + N

Once it works, proceed to your regular browser and clear its cache to refresh your website's preferences. Also, you may use another supported browser, as the current version of QuickBooks you're using might be experiencing a temporary malfunction. 

Additionally, I'll provide these articles to help you learn how to record and receive invoice payments and to understand more about the different file types that you can attach to any transactions in QuickBooks Online:

• Record invoice payments in QuickBooks Online.
• Add or delete attachments in QuickBooks Online.

Feel free to ask by adding a comment below if you have any concerns about managing your invoices or any other issues. I'm here to help 24/7. Wishing you and your business continued success.