Hello, Good day.
We have made a test order and uploaded the receipt.
The thing is, Receipt uploads Successfully and Completely but the reason you get error is because of these error lines:
<b>Warning</b>: Object of class Automattic\WooCommerce\Admin\Overrides\Order could not be converted to int in <b>/home/u612287972/domains/jcstoreccs.com/public_html/wp-includes/post.php</b> on line <b>6590</b><br />
<br />
<b>Warning</b>: Object of class Automattic\WooCommerce\Admin\Overrides\Order could not be converted to int in <b>/home/u612287972/domains/jcstoreccs.com/public_html/wp-includes/post.php</b> on line <b>6510</b><br />
You can check it out yourself, just open your browser’s console and find Network Tab, then select your receipt and hit Upload, see the result of the Request, you’ll see this error.
The solution could be turning off your error display.
And because you are using wp.com CDN, disable Secure Link from Upload Receipt Plugin Setting.