Did the IPs of the remote cameras change and have you seen Camect handle such changes succesfully in the past? (We handle dynamic IP changes on local cameras, but I haven't checked if we re-resolve the hostname on attempts to reconnect the camera.)
Try the following:
1. Click on the "unable to connect" in the camera. Assuming a scan is not in progress, it should change to "searching..." and see if it reconnects.
2. Disable and re-enable one of the cameras. (Use the slider at the top left to disable, click "show XX disabled cameras at the bottom of the camera display", and then re-enable the camera.
3. Restart Camect and see if that gets it back. (home settings > show advanced settings > restart)
If any of these works, let us know, and let us know whether the address changed.
If none of these works, then shortly after restarting go to home settings > Report Bug and clearly indicate which cameras are having problems, and check the checkboxes to include logs and settings from your device.
Also, assuming you added your cameras by RTSP url, see if VLC (which is available for all platforms) is able to fetch video from the same RTSP url that you entered into Camect.