I’m unable to provide a direct download link for “ds7616nik2 firmware” because:
Sequential Updates: If your current firmware is very old, do not jump to the latest version immediately. Update in steps as recommended by experts at use-IP LTD to prevent software glitches.
Hikvision Europe Download Portal (Navigate to Product Firmware > NVR > K-Series) How to Identify Your Current Version
Never jump versions: If your device is running a very old version, do not flash the newest build immediately. Update sequentially through the major bridge versions (e.g., v3.xx to v4.xx) to avoid software corruption.