While duplicating an SSRS report for customization sometimes you may face this error at the time of report deployment.
"SSRS Report Deployment failed - The number of the defined parameters is not equal to the number of cell definitions in the parameter panel."
The first thing you need to check for any extra parameter is this report, compare with the standard report. There are two places you need to compare
1. DataSet parameters
2. Report Parameter
There might be an extra parameter(s), try to remove this extra parameter from the report. In case you are unable to delete it from the front end you need to open the report in XML (Right-click on the report in solution and select open with > Open with XML Text editor).
In the XML file search for this parameter and carefully remove it from everywhere. If you are not familiar with XML better to take help. Save your changes and build the solution. This time your report should be deployed without any error.