I have create a report using visual studio 2015 with SSDT Tools installed from the following link
https://msdn.microsoft.com/en-us/mt186501
The database is on SQL Server 2014. The reports work on my machine however when I try to upload a report on customers machine(Which has SQL Server 2014 and not visual studio). I get the following error
"The definition of this report is not valid or supported by this version of Reporting Services. The report definition may have been created with a later version of Reporting Services, or contain content that is not well-formed or not valid based on Reporting Services schemas. Details: The report definition has an invalid target namespace 'http://schemas.microsoft.com/sqlserver/reporting/2016/01/reportdefinition' which cannot be upgraded. (rsInvalidReportDefinition)"
If you have the solution > properties > TargetServerVersion set to SQL Server 2008 R2, 2012 or 2014 and then upload the RDL from the bin folder instead of the project folder, it should work. I was getting the same error and that solved it.