So, working on SSRS reports and your consultant informs you that, when they try to run specific reports, they keep getting "Error while setting server report parameters. Error message: The permissions granted to user 'domain\icordobin' are insufficient for performing this operation. (rsAccessDenied)".
If you connect with your user, you might see that the report(s) run properly.
As the issue's message states this is indeed a security issue, but it may fail to catch your attention at first. The way I had the setup done, was that initially only an Admin group had access to the reports (the SSRS security at http://localhost/Reports) and then I added the AX Functional group. I also went in the DynamicsAX folder and reverted the security to match its parent.
The only item that I didn't pay attention was that the StaticReports subfolder security's (yes, you should see it in your DynamicsAX folder, if you don't you have another problem) didn't reverted back to match its parent when doing the step above (I think this happened because initially I broke the cascading security at the DynamicsAX folder by altering there the security). So, I was left with some of the most important reports in AX (FreeTextInvoice, PurchPackingSlip, PurchPurchaseOrder, SalesConfirm, SalesInvoice, Sales* ...) with the initial security. Voila, an AX consultant will have no access to these.
Do change the security on the StaticReports folder and it will start to work.