Can you try changing the port number of HTTP as below and check?
#set system services web-management http port 2222
#commit
then http://192.168.1.1:2222
You may also try below steps
1. > restart web-management
2. #deactivate system services web-management
#commit
#activate system services web-management
#commit
3. reboot the device if the above 2 didnt help