It is possible to be able to see a camera in Matrix by right-clicking>>view even if it has the red-x icon next to it. The red-x indicates that there is a problem with recording. You may be able to view the camera in matrix using Internet Explorer because it is pulling the live view stream directly from the camera. This means that your computer is able to pull the stream from the camera itself.
First place to start when troubleshooting this recording issue would be to go to the archive server and try to navigate to the cameras interface. After you confirm this is not a network or camera related issue (meaning you can see the camera's live view from the interface). Go to the ESM Admin interface and double-check the settings. Common issues include incorrect authentication, incorrect camera model selected, no archive server or archive server volume selected, and the enabled button not checked.
ESM is on a delayed time to try to reconnect to the camera once it fails repeatedly. You may just need to wait after correcting issue in the ESM Admin interface for ESM to retry the process to successfully connect again.
If you have confirmed all of the above and are still experiencing issues. please feel free to request additional support by emailing firstname.lastname@example.org.