The router is using port 80 for its HTTP management page as well as the firewall blocking page. Below are the configuration required for turning off TCP port 80 for the router.
You can do this from System Maintenance >> Management >> Management Port Setup. However, if you're not using the default HTTP port, remember to specify the port number when accessing the management page (for the configuration below, you will need to type 192.168.1.1:88 in the address bar instead)
You can disable the block page can by typing the command
csm dnsf blockpage off. Then,
sys reboot to restart the router.
However, if you turn off the block page, instead of being noticed that the page is blocking by the router, users will only see that the page is not working.