The trial is a fully functional and feature complete version of Highcharts that expires after 30 days of usage. The licensed version of Highcharts is identical in every way to the trial with the exception that it never expires. The only thing that is needed to replace the Trial with Licensed version is to add serial key to Web.config file into appSettings section with key = "Highcharts". Example: <add key="Highcharts" value="PlaceForSerialKey"/>
For .NET Core serial key should be placed on the highest level in appsettings.json file ("Highcharts": "PlaceForSerialKey"). Third parameter in HighchartsRenderer or HighstockRenderer should be set on true like here: var renderer = new HighstockRenderer(OptionsObject,null,true). Three packages should be added: Microsoft.Extensions.Configuration, Microsoft.Extensions.Configuration.FileExtensions, Microsoft.Extensions.Configuration.Json
Alternative solution is to pass serial key as argument of HighchartsRenderer or HighstockRenderer constructor like here var renderer = new HighstockRenderer(chartOptions,"SerialKey");