Hello there, @alex.heath.light.

You can add a logo to your invoice from the Custom form style page.

Here's how:

1. Go to the Gear icon.
2.  Choose Custom Form Styles from the pop-up window.
3. Locate the invoice template and hit Edit under the Action column.
4. Under the Design tab, hit the Make logo Edits section.
5. Click the Plus sign icon and select the file.
6. Hit Save, then Done.

In the meantime, once you change the file type of your logo, and upload it again. I'd suggest reaching out to your IT personnel or the one who creates the logo. They know how to manage it.

I'm adding articles for more details about logo and transaction templates:

• Add, customise, or remove logos on sales forms.
• Customise your invoices, estimates, and sales receipts in QuickBooks Online.

Please let me know how everything turns out. I'm always here to keep helping. Have a good one!