Getting "an error occurred while downloading your invoice id" on the billing page

Hello.

As per the error message, will you be able to download it if you access it after a while?
I don't think it's very relevant, but do you have an IAM policy in place to display invoices to the IAM users you're using?
In some cases, there may be a problem with your AWS account, so we recommend that you open a case with AWS Support under "Account and billing".
https://docs.aws.amazon.com/awssupport/latest/user/case-management.html