Looking at the .har file collected while reproducing the issue, it can be seen there are errors 403 which are logged randomly, not always the same request for data.
Investigating on those errors 403 in the IIS logs, it can be seen there is a sub error code which 501 like (some data removed or modified) this entry:

2025-09-23 12:05:49 10.246.43.14 POST /Director/service.svc/web/GetBrokerLicenseStatusesData - 443 - IP_ADDRESS HTTP/2 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/140.0.0.0+Safari/537.36+Edg/140.0.0.0 https://FQDN%2fDirector%2fdashboard%3flocale%3den%5fGB%26siteid%3d96f00e5d%2d60b9%2d4e58%2d89ab%2d7539cdcd7ae9& 403 501 0 21

This error code "403 501" can be a sign requests are rejected because of Dynamic IP Restriction settings being enabled.

When IIS “Deny IP Address based on the number of concurrent requests” is set wit its default value of 5, some requests are dropped with HTTP error code of 403 501 which causes Director dashboard not to load properly.

Disabling “Deny IP Address based on the number of concurrent requests” fixed the issue.
If enabling “Deny IP Address based on the number of concurrent requests” is a mandatory Security request, please consider testing higher values than 5 which is the default.
The IIS setting linked to this is denyByConcurrentRequests.

When “Deny IP Address based on the number of concurrent requests” is configured at IIS level with its default value of 5, Director dashboard does not display properly.
Instead of the data appearing, the dashboard displays spinning wheel for some of the fields. This setting can be found under IIS Manager "IP Address and Domain Restrictions".