Thanks for all the input. I discovered what is causing the error. When configuring the camera, I activated the IP filter, entered the IP addresses that I use to enable remote viewing which apparently caused the snapshot notification to fail. With the IP filter disabled, snapshot notification worked first time. This is somewhat puzzling as i thought the IP filtering was only supposed to allow/deny specific addresses/subnets etc from accessing the camera. I also discovered that with IP filtering enabled and using the mydlink app, the camera is listed as offline even though the IP address of the tablet is in the allow list of IP filtering.