After upgrading a K2 Five version, users under a configured Active Directory sub-domain may be unable to sign into K2 (no error thrown).
This error can occur if the LDAP string is modified. If the behavior is occurring following an upgrade, run the following query to check the configuration for the RoleInit value:
SELECT * FROM [HostServer].[SecurityLabel] WHERE SecurityLabelName = 'K2';
If there is an incorrect value here, please update the LDAP string for the sub-domain in K2 Management -> Users -> K2 -> Domains.