Getting an error on redeployment of a report to SSRS 2008

I have taken over working on some reports in SSRS an am fairly new to the platform. I have the original report in Visual Studio 2015. I have made the changes and tested it in this environment with no errors. However, when I deploy it to the server and try to run it from there I get the following errors:

• An error has occurred during report processing. (rsProcessingAborted)
  • Query execution failed for dataset 'getData'. (rsErrorExecutingCommand)
  • Must declare the scalar variable "@startDate".

My issue in working this out is that the modifications that I have done do not include any of the queries or any of the parameters, all I have done is move some tablix around on the page and modify the filters for these.

I have gone into Manage the report on the server and compared this between the working old report and the new report. I have had a look at the XML version of the report and can find no differences in the parameter/query section of the report.

Any suggestions on what to look for? Happy to post the XML here if needed.