This error means the API key has reached the DIEM spend limit configured for that key.
First, confirm you are logged into the account that actually holds your DIEM. A common cause is creating an API key on a different account (or a different login method) than the one where your DIEM is staked, so the key has no DIEM behind it. Check the account email in Settings and your staked balance.
Review the key's spending-limit settings at venice.ai/settings/api. If the key was meant to have no DIEM spend limit, adjust the limit or create a new key with the intended settings and test again.
If the error continues on the correct account with a correctly configured key, contact support and describe the issue. Do not share the API key itself in any message.