After the update completes, perform a factory reset to clear any residual previous settings:
Open a browser (Chrome/Firefox/Edge – avoid Safari on Windows) and go to http://192.168.0.1 . Enter your admin password. d-link dwr-921 latest firmware
Regarding Security patch for your D-Link Devices Firmware updates address the security vulnerabilities in affected D-Link devices. DWR‑921 - 4G LTE Router - DLink After the update completes, perform a factory reset