It's good to see you here in the Community, @melissas-marines.
I'd love to help you with your concern, but can you please share the exact error message after sending the invoice? Also, can you provide a screenshot of the Customer Center view you're referring to? This will help us provide the best resolution to your concern.
The Community team and I will be standing by for your response so we can address your concern. Wishing you all the best!