Enum describing possible incentive errors.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v23/errors/incentive_error.proto)

| Enums ||
|---|---|
| ## `ACCOUNT_TOO_OLD` | This incentive cannot be applied because too much time has passed since the account's first ad impression. |
| ## `INVALID_INCENTIVE_ID` | The incentive ID is either invalid or not supported for the given country. |
| ## `MAX_INCENTIVES_REDEEMED` | The maximum number of coupons has been redeemed. |
| ## `UNKNOWN` | The received error code is not known in this version. |
| ## `UNSPECIFIED` | Enum unspecified. |