I cannot save invoice templates

Welcome to the Community, @maryna-alpha-plu. It's my priority to help you save your invoice template in QuickBooks Online (QBO).

The stored cache on the browser you're using can affect this issue. To isolate this behavior, I'd recommend accessing your account using a private browser and saving your designs from there.

You can use either of these keyboard shortcuts to save you time:

• Google Chrome: press Ctrl + Shift + N 
• Mozilla Firefox: press Ctrl + Shift + P 
• Safari: press Command + Shift + N

If it works, clear the cache of your main browser to remove browser history. You can also use other supported browsers to narrow down the result.

For additional resources, while modifying your invoice templates in QBO, you can also check out this article: Customise invoices, quotes, and sales receipts in QuickBooks Online.

Additionally, you can get more tips while handling your other customer transactions from our self-help articles.

If you have any other questions while working with your templates, let me know by adding a comment below. I'm more than happy to help. Have a good one!