I have cameras installed in a very rural area that has poor internet access. I recently changed ISPs, from Suddenlink to ATT Cellular, and I no longer receive motion alerts, nor do the cameras record. I'm using an ATT Cellular modem (model MF279) that supports wireless and includes an Ethernet port. The four Amcrest cameras are all IP2M-841B. I am able to view video on all cameras, but I no longer receive motion alerts, nor do any of the cameras record video through the Amcrest Cloud when motion occurs. I use the Amcrest cloud service to view all videos and recordings.
However, when I connect the cameras to a network from another ISP, everything works fine. So far, I have tried two other ISPs, and video, motion detection, and recording all work fine when viewed through the Amcrest cloud service.
At the rural site with ATT cellular, I have disconnected all other devices so that there is only a camera connected to the cellular modem, but there is no change in the behavior. I have not yet tried static IP addresses or port forwarding, but I would be happy to try if anyone has recommendations. There must be some type of "handshaking" that occurs between the cameras and the cloud service that is being blocked or interrupted by ATT cellular or by the cellular modem. I would also be happy to try other recording apps or services that might be recommended.