Active Directory – Oracle Cloud: The Windows instance does not automatically join the domain

Let me explain my configuration. My VCN has two private subnets.

Subnet 1: The domain controller installed with the required AD ports is opened through the security list on subnet 1. It uses the default DHCP options. DNS role installed on the same server.

Subnet 2: Windows instance installed with the custom DHCP option, where the custom DNS points to the server what I have installed in subnet 1.

Issue: When the Windows instance is deployed in subnet 2, it remains in the workgroup that does not automatically join the domain. Each time, I have to add it manually.

Note: The domain controller, the DNS server, and the test computer can communicate between subnets. Please help me on how to load the machine with the joined domain.