SQL Server Error 13805, Severity 17 corresponds to encryption issues or problems encountered while working with cryptographic providers. This error message is associated with a key handling problem when SQL Server tries to use an Extensible Key Management (EKM) provider for encryption or decryption operations. A typical scenario involves misconfiguration or connection issues between SQL Server and the external EKM module.

Severity 17 indicates that this is not a user-level problem, but rather something caused by resource constraints, incorrect configurations, or environmental failures.

Common causes: 

• Improper Configuration of Cryptographic Providers: The cryptographic provider details may be incorrectly configured in SQL Server, resulting in communication errors.     
• Missing External Libraries/Drivers: If using an external Extensible Key Management device (e.g., Hardware Security Module), necessary libraries/drivers may not be installed on the server.  
• Connectivity Issues With EKM Provider Service: Network-related issues could block communication between your database instance and the external security devices/services.     
• Permission Problems: The account running the SQL Server service might lack proper privileges required for accessing keys from the cryptographic provider. 
• Provider Timeout Or Misconfigured Algorithms: Incorrect algorithms specified during setup can cause incompatibility that results in failure during encryption/decryption attempts. 

Guidance for Troubleshooting:  

Verify Current Configuration Run T-SQL queries against system views related to Cryptographic Providers. List all registered cryptographic providers.

SELECT * FROM sys.dm_crypt_provider_properties;

Check current Encrypted Symmetric Keys status.

SELECT * FROM sys.symmetric_keys;

Validate if there are any discrepancies such as missing properties (`module_path`) or unused entries which may indicate stale configuration settings. 

Check Encryption Algorithm Compatibility Ensure that you’re using a compatible algorithm supported by both SQL Server and your specific EKM/crypto-provider setup. Example Encryption Setup Validation Query: 

CREATE SYMMETRIC KEY <KeyName> WITH ALGORITHM = AES_256  
ENCRYPTION BY PROVIDER MY_CRYPT_PROVIDER_NAME; 

If this query fails with error code 13805, there’s likely a compatibility issue at play; consult documentation from your crypto-provider vendor.

Validate Permissions For Service Account The Windows account under which MSSQLSERVER runs must have adequate permissions to access resources needed by third-party plugins/libraries involved here!