Applications for the Bootcamp work mainly on a first come, first serve basis. If you were unsuccessful it likely means that all the spots are already filled.
The following will also result in an unsuccessful application:
If you are a Government/Government Agency
If your end-users are not located in one of the regions where the Bootcamps are focusing on
If your use-case is not suitable for WhatsApp or violates any WhatsApp policy.
If your organization does not do social-impact work.