Security Cameras Offline Status / Ethernet Connection to XFi modem router

Have an xfinity modem router with Ethernet connection to my not xfinity security cameras. Worked great for long time. Noticed something up when I couldn’t get the cameras on my cell phone anymore. No ipv4 address / status is offline. Wifi and all that still good. Tried changing to other Ethernet ports on back of modem. No luck. Have not tried changing Ethernet cord yet because it’s shimmied up into the attic and etc. which I realize could be part of the problem. Any help greatly appreciated.