rsAccessDenied Error even though all users are granted ALL Roles (TfsReports on SQL 2014)

We have granted everyone all roles on our TfsReports site. However, the users still get the following errors when attempting to manage the reports:

"The permissions granted to user Domain\UserName are insufficient for performing this operation. (rsAccessDenied)"

These are the roles we've granted to all "Domain Users": Browser, Content Manager, My Reports, Publisher, Report Builder, Team Foundation Content Manager.

We can't seem to figure out what else might be missing.

Please help.