Please refer to the information from the following KB article: Font is missing in report designers.
The desktop Report Designers need the assembly Microsoft.mshtml for the HtmlTextBox designer. The assembly can be found by default in the Global Assembly Cache of most Windows OS. The Windows Server Operating Systems lack the specified assembly and for that reason the designers crash on these systems, with an error message indicating that the assembly is missing.
The Reporting engine and the Telerik Reporting REST Services work correctly also on Windows Server Operating Systems. Hence, the Windows Server OS can be used for deploying Telerik Reporting projects. For designing reports it is necessary to use Windows OS editions for personal computers like Windows 10.