Hello, friend!
Based on the screenshots you provided, I will compare the WebUI of the HG8245H5 with that of the general-purpose HG8245H5.
There are two possibilities:
The account you have logged in to does not meet the permission requirements. You need an administrator account to perform device configuration operations.
This device is a carrier-customized device. This function may be disabled due to local ISP customization requirements. Contact the local ISP for a detailed solution.
Thanks!