Hi Anis,
Thanks for using Syncfusion products,
We have checked your given screenshot, and we are unable to reproduce the reported issue with windows server 2012. We have created and attached the simple Spreadsheet MVC sample, could you please try the attached sample and get back to us with more information or by reproducing the issue in the below sample.
Also please share the information like windows server configuration and if possible please share the issue replicable sample with us. So, that we can work on this and provide you a better solution quickly.
Regards,
Shanmugaraja K