Thanks MaryLandT,
I actually tried that, I get the message :"We currently support issues related to the API only. For UI issues, visit the QuickBooks Community for help." :)
You're welcome, @userjosh-intuit.
I have another idea on how to get you going with your forwarding receipts concern.
The Community site can only assist with QuickBooks-specific issues. Since you have a sandbox account, I suggest visiting the Intuit Developer page. They can provide more insights why you're unable to forward receipts using your sandbox account through QuickBooks Online.
To ensure you'll get the right support team, here's a link you can use: Contact QuickBooks Sandbox. Click the Ask a Question button, and then enter your concern, like "Unable to forward receipts in QuickBooks using my sandbox account". 
When you're all set, you can start categorizing and matching your receipts. Doing so helps ensure they go to the right accounts and prevent any duplicates.
Stay in touch with me if you have additional questions about sending receipts. I'm here to answer them for you.
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