Directory issue

Port 53 is a DNS lookup port. It sounds like there is a requirement that is missing for your to build the AD Connector.

Please give a read to the AD Connector Prerequisites.

https://docs.aws.amazon.com/directoryservice/latest/admin-guide/prereq_connector.html

See?

Ports for subnets

For AD Connector to redirect directory requests to your existing Active Directory domain controllers, the firewall for your existing network must have the following ports open to the CIDRs for both subnets in your Amazon VPC.
    TCP/UDP 53 - DNS
    TCP/UDP 88 - Kerberos authentication
    TCP/UDP 389 - LDAP

Let me know if you have any issues with this, or if it helps you then please accept my answer after you've tried it out - it would be much appreciated! Good luck :)