The logo I use was working fine. Now, for some reason it has Shrunk. It looks fine on the example but now appears way too small. Enlarging the image doesn't help or fix

Hello there, roger4.

Let me welcome you first to the Online Community. Thanks for bringing this to our attention.

I’m here to provide information on why the invoice logo's size is showing small.

This is a known issue, and our engineers are working towards finding a permanent solution. I want to make sure you'll get looped in to any updates about the progress, so I suggest you contact our Customer Care Team.

One of our specialists will gather your information in a secure environment and add you to the notification list. You can reach them by following these steps.

1. Go to Help at the top, then click on the Contact Us link.
2. In the How can we help? window, enter contact support in the field box.
3. Select Let’s talk.
4. Choose a way to connect with us.
5. Select Chat or Call us.

For future reference, I'm adding an article with tips and tricks about customising a logo: How to add, customise, and troubleshoot logo on sales forms.

This information should point you in the right direction. 

Reach out to me if you have questions about QBO. Please know I’m just a comment away for help.