The version of the report server database is either in a format that is not valid, or it cannot be read. The found version is '163'. The expected version is '162'. (rsInvalidReportServerDatabase)
1. Verify the ReportServer Database compatibility.
2. Change the Compatibility to previous version and restart the services.
3. If the above fails check the RSEXEC role has been granted for the DBO
4. If above is already in place then it could be the latest security patch applied on the SQL Server.
5. Verify any CU/Hotfix which has been applied and caused the issue.
6. Rollback the patch or if its on cluster apply the same patch on the other node too.
Note: Even though SSRS is not a cluster aware component But this security patch will also apply on the SQL Server and makes SSRS to stop working.