Event ID - 646

Event Id646
SourceMicrosoft-Windows-ADFS
DescriptionThe Federation Service encountered an error while loading the trust policy. The trust policy field '%1' is empty. 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 should occur only if the trust policy file has been modified without use of the AD FS administrative tools. Add data to the '%1' field.
Event Information According to Microsoft :

Cause :

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

Resolution :
Review the script for creating the trust policy

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

Check the script for creating the trust policy. Make sure 0 length of string (null or empty string) is not passed as the argument to any functions that are exposed by the trust policy object model.

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 646 from Source Microsoft-Windows-ADFS

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