DIAGNOSIS This is a UPNP or port forwarding issue. The camera cannot establish a direct connection (P2P) to your phone over the internet.
FIX First, ensure the camera and your phone have a stable internet connection. Restart your home router. In the Reolink app, go to Device Settings > Network > Port Settings. Ensure 'UPnP' is enabled. If it is, try disabling it, saving, then re-enabling it.
IF THAT DIDN'T WORK Your internet service provider (ISP) or router may be blocking P2P traffic. You may need to manually set up port forwarding on your router for the camera's IP address and ports (e.g., 9000, 37777). Consult Reolink's support site for the specific ports.
HEADS UP Watching live view away from home uses significant data on your phone plan. It also drains the camera's battery much faster than when locally connected.