Your router may be changing the camera's IP address if you have selected DHCP network setting. Change instead of fixed IP address.
If your camera is connected via WIFI you should be aware that a standard router can send a signal up to 10m in open air. If there are walls between the camera and router, reducing the distance. Therefore, try to amplify your WIFI with an extender or connect your camera to your router with a network cable. Br>
Alternatively, the problem may be that your router releases the address for use with other devices if there has been no activity on the camera. Check with your router vendor on the camera can be registered to the router with a fixed connection. Br>