Hi khanguyen,
I'm sorry to hear that you're experiencing issues saving invoices, and I'd like to help get this resolved.
First, try clearing your browser's cache and cookies, then log in again. If you're using the mobile app, make sure it's updated to the latest version and try logging out and back in. You can also test using different browser or device to see if the issue persists. Additionally, you need to double check your user permissions to ensure your role is correctly assigned, even as an owner/admin. Set up roles has detailed instructions to assist you.
If the issue continues, it's best to reach out to our live chat support through our virtual assistant MOCA or submit a case via MyAccount, and they can check your account on their end.
Regards,
Sai