: Some versions of SmartPSS (notably v2.002) have a known bug with the dhnetsdk.dll file that causes playback to fail even when the timeline shows recorded footage. You can fix this by downloading a newer version of the dhnetsdk.dll file and replacing it in the installation folder (usually C:\Program Files\Smart Professional Surveillance System\SmartPSS ).
Ensure both the SmartPSS software and the NVR firmware are up to date. Manufacturers frequently release patches for SDK communication errors. Prevention and Best Practices
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: Completely uninstalling the current version and reinstalling the latest version with administrative privileges can often clear buggy SDK configurations. Technical Context