Hi, We developed reports in Visual studio 2015 and trying to deploy in SQL 2014 (RTM) Report Manager but having compatibility issues. VS 2012 reports are working fine. is it known issue? how about applying SP1 to SQL 2014? I think SQL 2016 is not yet released.
As far as I know, you should be using VS2013 or VS2012 for SSRS 2014. VS2015 will be for SSRS 2016 which hasn't been released yet.
Agree with Tara. It's about the compatibility. VS 2015 only works with sql 2016 Data Tools.