Asset Scan problem

Asset Scan problem

We installed Asset Explorer Agent of all computers in our AD computer through a GPO, and it works fine for most of our asset except a few. The first scanning after asset explorer agent installation was successfully finished for some assets.. But, if we try to scan it again from Windows Domain Scan or from asset itself, it gives this error:
FAILURE :Failed to communicate the agent.

with imported assets.. it gives this error:
FAILURE :No response received from workstation. Probably the workstation might be switched off or does not exist.
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