Same issue is here, I can trigger job with 2.1 config by github pushing, but via API is not working, not supported yet?
Build-agent version 0.1.900-892a9f73 (2018-10-25T15:49:42+0000)
Configuration errors: 2 errors occurred:
* Configuration version 2.1 requires the "Enable Build Processing" project setting. Enable Build Processing under Project Settings -> Advanced Settings. In order to retrigger build processing, you must push a new commit.