The report server cannot decrypt the symmetric key that is used to access sensitive or encrypted data in a report server database.

I got the following error when trying to use SQL Server Reporting Services manager:

The report server cannot decrypt the symmetric key that is used to access sensitive or encrypted data in a report server database. You must either restore a backup key or delete all encrypted content. (rsReportServerDisabled) Get Online Help
Bad Data. (Exception from HRESULT: 0x80090005)

Solution:

You will need to reset your encryption keys. To do that:

1. Open Reporting Services Configuration Manager and select 'Encryption keys' tab


2. Click 'Delete' in 'Delete Encrypted Keys' section:
   
   
3. You will need to reset all connection strings and db credentials for all your data sources