The report server cannot access the private key for the service account. This key is used to decrypt the symmetric key that protects content in the report server database… (rsKeyStateNotValid)…
Key not valid for use in specified state. (Exception from HRESULT: 0x8009000B)
This is because you’ve changed the private key in SQL Server Reporting Services. This may have been done because you restored Reporting Services but not restored the private key, or some other reason.
To fix this either:
Open Reporting Services Configuration Manager, click Encryption Keys and delete the existing encryption keys and create new ones. You will lose all the subscriptions to reports if you do this
Restore a backup of Reporting Services to another location (keeping the current one intact), click Encryption Keys in Reporting Services Configuration Manager and Export the keys. On the original Reporting Services server, open Reporting Services Configuration Manager and import the encryption keys you have just exported