Error registering the viewer with the service. An error has occurred. Access to the path 'C:\Windows\TEMP\TelerikReporting\16.0.22.225\LCT\value.dat' is denied.

[Khadeer]

I have added the Startup page screenshot . I am getting the above error. Please suggest to resolve the issue 

[Neli]

Hi Khadeer,

I am sorry for the issue that you are experiencing. 

The error message "Access to the path X is denied" indicates that the Reporting REST service cannot access the configured file storage. By default, the user temp folder will be used as storage which is 'C:\Windows\TEMP' in this case. 
You can change the default folder using the second overload of the FileStorage and passing the custom folder location. The changes need to be made in ReportsController.cs file where the settings of the Reporting REST service are defined. Please refer to this excellent knowledge base article for an example - Error registering the viewer with the service. Access to path X is denied.

Make sure that the IIS process has read/write access for the folder used by the storage. You can give access to the folder from its Properties - Sharing|Security options or change the used application pool's Identity through IIS Manager.

In case you have different instances of the application running, set a unique HostAppId for each instance of the Reporting REST Service. The settings must be added in the ReportsControllerBase implementation.
Depending on the hosting environment, you should also consider the appropriate cache storage options - please check the available options in REST Service Storage.

In case the issue persists please send us a sample project that demonstrates the current settings of the viewer and Reporting REST service and more details about the hosting environment, so we can investigate further.