SSRS : Bug using SSL (https://)
Well, it was difficult to solve, but with the help of our sysadmin and reading through lot of places, we managed to get it working. It was a mix of things, but the 2 main ones were changing some parameters on SSRS config file:


Change &lt;Add Key="SecureConnectionLevel" Value="0"/&gt; to &lt;Add Key="SecureConnectionLevel" Value="3"/&gt;
Make sure that &lt;RSWindowsNTLM/&gt; is the only authentication type specified
on &lt;AuthenticationTypes&gt;
make sure all url's are absolute, without wildcards


And second part was to modify a windows registry and restart SSRS afterwards:

Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa

Create a new DWORD registry key DisableLoopbackCheck and set value to 1.

In case you are wondering, here are all the references consulted:


https://social.msdn.microsoft.com/Forums/sqlserver/en-US/2d216af4-6586-4619-b8aa-56f05cbd8239/the-request-failed-with-http-status-401-unauthorized-in-ssrs?forum=sqlreportingservices
https://connect.microsoft.com/SQLServer/feedback/details/323214/the-request-failed-with-http-status-401-unauthorized
https://social.technet.microsoft.com/Forums/en-US/27ecdb2d-d6be-4e10-a7e2-7fedba1266e2/url-problems-with-sql-server-reporting-services-2012-with-wildcard-ssl-certificate?forum=sqlreportingservices
https://www.sqlservercentral.com/Forums/Topic908027-146-1.aspx
http://sqlmag.com/sql-server-reporting-services/implement-kerberos-delegation-ssrs
https://msdn.microsoft.com/en-us/library/cc281382.aspx