We have a Cisco modem/router model DPC3941B provided to us by Comcast.  This modem will not give IP addresses to devices which are not running Windows (such as Ipads, Iphones, Tablets, etc); the modem recognizes the devices but will not give them IP addresses so these devices cannot access the Internet.  The devices access the modem thru our WIFI system using UNIFI Access Point Pro.  Laptops running Windows access the modem thru these same access points and work just fine; the modem recognizes the devices and gives them IP addresses.  

Please help me solve this problem.  I will appreciate any kind of help or suggestions.