NetpJoinDomainOnDs: Function exits with status of: 0x216d
0x216d = ERROR_DS_MACHINE_ACCOUNT_QUOTA_EXCEEDED
“Your computer could not be joined to the domain. You have exceeded the maximum number of computer accounts you are allowed to create in this domain. Contact your system administrator to have this limit reset or increased.”
By default any authenticated user can add up to 10 workstations to the domain.
After that you need the appropriate rights.
You can either get the rights delegated (recommended) or increase the default limit for authenticated users (not recommended).