Enum describing possible Demand Gen campaign errors.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/errors/demand_gen_campaign_error.proto)

| Enums ||
|---|---|
| ## `CANNOT_ACTIVATE_MIGRATED_CAMPAIGN` | Cannot activate a migrated campaign before the original campaign is removed. In addition, only one migrated campaign for each original campaign can be activated at a time. |
| ## `UNKNOWN` | The received error code is not known in this version. |
| ## `UNSPECIFIED` | Enum unspecified. |