The administration site lacks any styling and just mainly contains the text.

Check your browser is not blocking our SSL-protected site.

URLs that should be enabled by your corporate firewall rules include

Use this site to test your browser SSL support

https://www.ssllabs.com/ssltest/viewMyClient.html

Ideally, you want to see something like this

If you see errors similar to the image below, contact your IT team to ask them to check their firewall setup