Door View Cam - camera does not work

I've just moved from one location to another and mounted my Door View Cam. Since that I re-set it up, it seems like a camera does not work. I see all activity happened in the app list, but any video could be opened. The device is online and up to date, the connection with internet is great. I have no idea how to check the camera itself so I would hear any advice from you. Thank in advance!