The Configure option is not visible in the Site Menu, there is no image shown, and the list of cameras is empty.
How this happens
This will occur if the Client had unpublished changes for a camera that was replaced via another Client. One such example would be the case where the Client on the processor had unpublished changes and a laptop was used to publish a camera replacement. In this case, the Client on the processor will exhibit the issue.
You will need to remove the unpublished changes as follows.
If this is happening on your laptop or a remote system, and you have the ability to reconnect to the Processor (make sure you know the IP address if it's remote), you can simply delete the site card and reconnect to the processor to add it back. Note that if you are connected to a local processor via its laptop port, you'll first need to close your laptop Client and disconnect from the processor before attempting to delete the site card because you cannot delete the local site card.
If this is happening onboard the processor:
Try not to leave the Client with unpublished changes. If the Client on the processor is used regularly via mouse and monitor, check to see that it has no unpublished changes, using Revert if necessary, before replacing a camera with a laptop Client.