in a lot of environments, due to the COVID situation there was spike in access to VPN based services, and in some situations slowness was observed in loading VPN / AAA Login page, to mitigate this problem some changes were done on httpd.conf file (https://support.citrix.com/article/CTX255947).
With a customized httpd.conf (for the above or any other reason), GUI issues can occur, an excerpt from the article below.
WARNING – Following the above solution might result in issues with future firmware upgrades.
When you apply the above configuration, the httpd.conf will not be updated during a future firmware upgrade. This could cause the GUI to become completely unavailable.
If this occurs, you must delete the file /nsconfig/httpd.conf (on both primary and then secondary node), reboot the ADC, and then reapply the below settings.
The clear diagnosis of that issue is that if you run “ps aux | grep httpd” in shell mode, there will be no httpd processes running.