Need to check them physically at each camera and make sure they are connecting to the main host router. Check the main host router for connected client devices. If there not listed there, then they've lost connection with the router.
Are these cameras in side?
Static IP addresses would be in the same string and what the Main host router gives connected devices using Dynamic IPs, accept that for static, the IP addresses are out side of the main host routers DHCP IP address pool, so if the pool is 192.168.0.100 to .200, setting cameras up for static IPs on EACH camera, you would set them to 192.168.0.93, .94, 95, 96 and so on up to .99.