I created some reports in Visual Studio 2015 with all the latest updates. However, when I try to deploy the reports I get this message:
The definition
I had the same issue when switching to VS2017 and installed Report Designer Version 14.2.
For me only 3 steps needed to fix the issue.
1: Set Change the xmlns to "http://schemas.microsoft.com/sqlserver/reporting/2008/01/reportdefinition"
2: Remove ReportSections" and "ReportSection" (Only Tags).
3: Remove report ReportParametersLayout section.
The only thing you need to memorize is to point xmlns to 2008/01
Other 2 steps can be seen in the error message after you change to 2008/01 and try to run the report.