@AbrarMasum 

Hi, thanks for posting question here.

Please kindly make sure that you need to add the correct client Mac address into the block list, some clients support the random Mac address function, it is recommended to disable this function on the client devices;

2.If there is VPN software on the client device, please disable VPN software first.

Also, Due to some special reasons such as application cache, security software protection, VPN encrypted connection, etc. Parental control may not be able to completely block some APPs and web pages. You may refer to the guide.