Does anyone know why I've received the message "Share this code with your expert 31881"?

Hello, @jenny45.

I suggest reaching out to our Customer Support team to check your account and verify why you've received this message. They have the tools to check your account in a safe and secure environment and verify this message.

You can do it by going to the Help icon at the top right of your QuickBooks Online (QBO) account. See this article for detailed guidance: Contact the QuickBooks Online Customer Support team. 

I'm always here if you need further help with your account. Have a great rest of the day!