Whenever a key file is generated on the Endpoint side, and Key Escrow is enabled (it is enabled by default) it creates a file called 'escrow' on the RBS Server in the user data folder.

This error might be caused because you are using the old key file. 

Go to this user data folder on the RBS Server machine, do a search for a file named 'escrow'.

Arrange the files with modified date/time. Find out the latest escrow file, if you have more than one file.

Compare the date/time of the latest escrow file with that of the key disk which you have and tried for disaster recovery. If they do not match, then that indicates that a new key is being generated on the client side which led to this new escrow file on the server.

As a Work Around:

Install the Endpoint either on the RBS Server Machine itself or on a PC locally connected to the RBS Server (Same LAN where the RBS Server is located) and Perform the Disaster Recovery procedure. You will need to Redirect the restores to a removable drive so you can ship the original data back to the client.

1. Create a new Endpoint installer with the Account Settings the same as the Endpoint, but change the Backup Server URL Address as below.

If the Endpoint is going to be installed on the RBS Server Machine itself, set the Backup Server URL to 127.0.0.1

If the Endpoint is going to be installed on a computer that is on the same local network as the RBS Server, the Backup Server URL should be the Local IP/Internal IP address of the RBS Server Machine. (192.x.x.x or 10.x.x.x)

2. Install the Endpoint using the New Endpoint Installer that you have created and perform the Disaster Recovery using the client Key Disk that you have.

Also See: What if a client forgets his encryption key? How does the Key Escrow process work?