If you installed SQL Server reporting Services (SSRS) on a server in a domain and you utilize a website user to start out the service and did not perform any further configuration, then you likely will only access the Report Manager using an IP and not the fully Qualified domain name (FQDN) of the server (if an SPN isn't set).

If you are trying to use the fully Qualified domain name to access reporting services then you may likely be prompted for username password several times ending with an empty page.

In order to be able to access reporting Services using FQDN you may need to perform the subsequent actions:
1. Register a Service Principal Name (SPN) for the Domain User Account that Runs SSRS
Please look at the following example:
sample computer name: testssrs01
sample domain: example.com
sample domain account: example\ssrsuser

Next, on the Domain Controller Server in a Command Prompt with Elevated Rights, you can Run as Administrator:
Example 1:
If SSRS are on port 80 (no need to specify 80 as it is the default http port):
Setspn -s http/testssrs01.example.com example\ssrsuser

Example 2:
If SSRS are on any other port (i.e. 2430):
Setspn -s http/testssrs01.example.com:2430 example\ssrsuser

2. Edit the RsReportServer.config File
On the Reporting Services server, in the virtual directory of SSRS, edit the "RsReportServer.config" file and locate the authenticationtypes section. Then add /rswindowsnegotiate as the first entry in the authenticationtypes section.

This above step will actually enable NTLM.

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