If the same thing happens, I'd suggest contacting our Customer Care Team. They can pull up your account in a secure environment and investigate what's causing this issue.
Go to the Help icon on the top right.
Enter your concern in the search field.
Choose Talk to a human.
Click the OK. To get you to the right human, in a few words, tell me what you need help with option and tap I still need a human.
Press Contact us.
Choose Message an agent or Get a callback.
In the meantime, just manually add the receipt by opening the expense transaction. Then, click on the Show existing link under the Attachment field. Once done, look for the receipt and tap the Add button.
To learn more about managing your receipts, check out these articles: