Could not connect to service. Key not valid for use in specified state (4042662)

Ranger GUI does not open after application upgrade or DB migration. Error thrown is "Could not connect to service".
There are additional details under Windows Event Viewer | Application and Services Logs | vRanger Service.

"vRanger Backup & Replication encountered an error during startup. The exact error message was: Key not valid for use in specified state."

"Could not connect to service" error is pretty frequent and there are multiple reason it is thrown. Most of them are related to the DB and some unexpected conditions. Here is few to check:

1. there are one or more records in DiskMount table. Table should be empty when vRanger services start.
2. there are one or more records in Credential table. It is not clear what this table is used for. Table is added in version 7.3.0 and usually does not contain any records. Table should be empty.
3. DB Connection string is stored in Windows registry still points to an old SQL instance.

Restart Ranger Services after any resolution.

Resolution #1. Run following  SQL commands:
USE vRangerPro
DELETE DiskMount

Resolution #2. Run following  SQL commands:
USE vRangerPro
DELETE Credential