If your organization has multiple domains, normally the AD service instance might register only 1 of it especially the ones for K2 service account or the one who installed / upgrade it.
After installation or upgrade, you can update the AD instance with the following sample for support of multiple domains.
LDAP:
| LDAP://DC=CompanyA,DC=COM;LDAP://DC=CompanyB,DC=COM;LDAP://DC=CompanyC,DC=COM |
NetBios
| CompanyA;CompanyB;CompanyC |
Separate each of the LDAP and Netbios with semi colon (;) End it up with no symbol
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