Error executing child request for /404 in a multisite SXA

Question

This is a multisite project built on SXA.

In the local instance, the pages load fine in both Preview & Experience Editor mode.

In the Site Grouping item for a site, the database is master and the VirtualFolder is cn.
But when I try to browse the live page https://myprojectsc.dev.local/cn, it shows this error:

ERROR Application error. Exception: System.Web.HttpException Message:
Error executing child request for /404. Source: System.Web    at
System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler,
TextWriter writer, Boolean preserveForm, Boolean setPreviousPage,
VirtualPath path, VirtualPath filePath, String physPath, Exception
error, String queryStringOverride)    at
System.Web.HttpServerUtility.Execute(String path, TextWriter writer,
Boolean preserveForm)    at
System.Web.HttpServerUtility.Transfer(String path, Boolean
preserveForm)    at System.Web.HttpServerUtility.Transfer(String path)
at
Sitecore.Pipelines.HttpRequest.ExecuteRequest.HandleItemNotFound(HttpRequestArgs
args)    at (Object , Object )    at
Sitecore.Pipelines.CorePipeline.Run(PipelineArgs args)    at
Sitecore.Pipelines.DefaultCorePipelineManager.Run(String pipelineName,
PipelineArgs args, String pipelineDomain, Boolean failIfNotExists)   
at Sitecore.Pipelines.DefaultCorePipelineManager.Run(String
pipelineName, PipelineArgs args, String pipelineDomain)    at
Sitecore.Web.RequestEventsHandler.OnPostAuthenticateRequest(HttpContextBase
context)    at
System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)   
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step,
Boolean& completedSynchronously)

Could this be due to the value for Virtual Folder field in Site Grouping item? Should I configure them somewhere else?