ISNet.WebUI.Webgrid version : 9.0.7200.1

While browsing on of our reports getting "WebGrid.NET - Unlicensed version"  error. But no issues while browsing other reports in the same application.

This report is pulling data from tables having 5lakh records and taking nearly 55 seconds for loading the data.

Is there any restrictions in webgrid for pulling large data from the tables? If the records are more how to handle the license error?