I can only suggest double checking the basics, i imagine you already have a successful AD integration, the syntax is case sensitive (Administrator is not equal to administrator), verify the netbios domain name, tha DA agent is being configured on a machine joined to AD domain. You can also check C:\ProgramData\CheckPoint\Logs\cpda.elg log file in order to see if you find any error after push operation fails.
If you already covered all of these, contact TAC should be next step.
One tip after you fix this problem. The target machine need to have all software requirements to install the agent correctly, for example SP1 on w7, .net framework 4.6.1, etc.
Regards