Event ID - 638

Event Id638
SourceMicrosoft-Windows-ADFS
DescriptionThe Federation Service encountered an error while loading the trust policy. An Active Directory Lightweight Directory Services (AD LDS) account store is configured improperly. A required configuration field '%1' is missing for the AD LDS store. Field: %1 If this error occurs during startup of the Federation Service, the Federation Service will be not be able to start, and all requests to the Federation Service will fail until the configuration is corrected. If this error occurs while the Federation Service is running, the Federation Service will continue to use the last trust policy that was loaded successfully. User Action This error should occur only if the trust policy file has been modified without use of the AD FS administrative tools. Add the missing field to the trust policy file.
Event Information According to Microsoft :

Cause :

This event is logged when the Federation Service encountered an error while loading the trust policy.

Resolution :

Add the missing field to the trust policy file

This error occurs only if the trust policy file has been modified without the use of the Active Directory Federation Services snap-in.

If you are using an Active Directory Lightweight Directory Services (AD LDS) account store, ensure that a value is provided in Search base Distinguished Name (DN) in the trust policy file.

To perform this procedure, you must be a member of the local Administrators group, or you must have been delegated the appropriate authority.

To provide a value in Search base Distinguished Name (DN)
  1. On the federation server, click Start , point to Administrative Tools , and then click Active Directory Federation Services .
  2. Double-click Federation Service , double-click Trust Policy , double-click My Organization , and then double-click Account Stores .
  3. Right-click the AD LDS account store whose search base you want to check, and then click Properties .
  4. On the Settings tab , in Search base Distinguished Name (DN) , add a distinguished name value, and then click OK .
Verify :

Verify that you can access the Active Directory Federation Services (AD FS)-enabled application from a client browser and that the resource can be accessed.
Reference LinksEvent ID 638 from Source Microsoft-Windows-ADFS

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