If you are using SSDT for Visual Studio 2015 or Visual Studio 2017 then most likely your SSIS Packages are designed to target SQL Server 2017 by default. If you are not deploying SSIS Packages to SQL 2017 then you must change TargetServerVersion as below.
For SQL Server 2017 (vNext) - SSDT BI for Visual Studio 2015/2017 (Apr 2017 Update or later)
- Install SSIS PowerPack.
- Launch Visual Studio 2015 or 2017. Create or Open your existing SSIS Solution.
- In the solution explorer, Right click on the SSIS Project Node and click Properties (This node may be one level below solution node as below screenshot).
- When you see Properties select Configuration Properties. You will see TargetServerVersion change that to other than vNext and click Yes if you see warning of Downgrade and then Click OK.