Here are the most common issues you might experience with billing:
My Google Billing Account does not appear in the Billing Management screen
Please verify that firstname.lastname@example.org appears as a Billing Account User on your Google Billing Account. Refer to instructions to add the Terra Billing Account User to your Google Billing Account in this article. After you add the Billing Account User, you should be able to create a Terra Billing Project.
Another reason you may not see your Google Billing Account is that you may have enabled Terra Billing permissions for the incorrect Google ID (e.g. Gmail address). This occasionally happens if you have both a professional Google account and a personal Google account, and you happen to be signed into your personal account. Please be sure to enable Terra Billing permissions for the Google ID under which you created your Google Billing Account. You may need to close your Terra session and/or log out of the incorrect Google account before re-enabling Terra Billing permissions.
When attempting to create a new Terra Billing Project, I see an error message indicating that a “resource has been exhausted”
This happens when you try to create a project but reached your Google quota. You may need to request additional projects from the Google Console as described in this Google Help article.
I see an error message related to an expired Google Billing Account trial
Google Billing Accounts set up using a free trial will automatically expire after 60 days unless you upgrade to a paid account. If your Google Billing Account expired, you will be unable to create a new Terra Billing Project. Log in to the Google Developers Console Billing page to verify that your Google Billing Account is active. You can select Show all accounts to display an expired Google Billing Account. If your Google Billing Account is "inactive" we suggest that you create a new Google Billing Account.