Bing Ads API version 13 (v13) has been available to all customers worldwide since April 2019. The API v12 documentation and SDK support was removed as of October 31, 2019. Starting from February 2020 calls to v12 may be returned with error 303 (ApiVersionNoLongerSupported). Upon completion of v12 sunset, only calls to v13 will be supported.
Please migrate to v13 services as soon as possible to avoid any disruption to your tools. The SDKs and code examples are already updated with support for v13. Please see the migration guide for full details and migrate soon to enjoy the benefits of this new API version.