“If the permission node under the design of the SSRS report seems OK you can try to export and re-import the SSRS report by XPO. For me, it solved the problem (on AX2012 R2 CU7) without having to add any permission on roles or privileges.
Under the hood, we found out that re-importing the report (re)generate data in the ModelSecurityPermission table of the model database, especially the permissions links between the report and the tables that it uses, and the data provider class.
AX / Dynamics 365 For Finance and Operations blog 