Permissions to connect to a 2016 report server

I have upgraded a web form application to be 2012. This application can currently call a report server that is 2008 or 2010 with no problem.

I am trying to get this application to connect to a report server 2016. I am getting the error message, 'The permissions granted to user 'X\User' are insufficient for performing this operation. (rsAccessDenied)'

I am running the web form application from my computer and localhost is being used.

The top of the web.config file looks like the following with values of 'xx' being the placeholder for the values.

Thus would you tell me what permissions are needed to solve this problem?

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