Hi,

So you have not changed service account since the cluster was started right? Can you connect to the passive node where it is failing and Check for "entropy" registry key in below Registry Node

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\ Security

If it is not present there then there is some issue in creating a new key upon failover. So two solutions at this stage.

1. Make Failover to passive node and stop and start the SQL Server (If possible :)) which should create a new key.

2. Run ALTER SERVICE MASTER KEY FORCE REGENERATE to create new key (Nothing wrong) which will re-encrypt all the contents.

3. Use BACKUP SERVICE MASTER KEY when the working node is active and make failover and then run RESTORE SERVICE MASTER KEY.

The Service Master key is combination of Service Account and Machine Account so if both are same then there should not be any issue. Please reply after try any of above methods.