Reporting Service 2014 Service Pack 1 Failing to work with error - wrong database version
There are two workarounds:

Delete one record from table ServerUpgradeHistory


USE [name_of_you_SSRS_database]
DELETE FROM ServerUpgradeHistory WHERE ServerVersion = 163


Install Cumulative Update 1 for SQL Server 2014 Service Pack 1. Before updating your SQL Server 2014 SP1 with Cumulative Update 1 - test it hard in your lab.

BE AWARE - Pay attention to backup encryption keys before you upgrade SSRS 2012 to
2014. After you apply CU1 all your encrypted content will be inaccessible.