Thanks for your response. You are getting this message because the license is not applied properly. Following could be the reasons behind this.
- You are applying the license but the path to license file is not correct
- Path to license file is correct but the application does not have the rights to access the file or the folder where the license file is located
You can enclose the apply license code in try catch block to check if you are getting any exception as shown in the following code sample.
using (FileStream licenseStream = new FileStream("LicenseFile.lic", FileMode.Open))
GroupDocs.Viewer.License lic = new GroupDocs.Viewer.License();
Hope it helps.