Did not find functions with language [dotnet-isolated].

We recently migrated our Azure Functions to isolated process (running on .NET 6). This was tested in our DEV subscription where there were no host level issues reported. However, in our production subscription, the functions 'intermittently' report the error "Did not find functions with language [dotnet-isolated].". What we have noticed also is that the function host is shut down. You need to then access the function through Azure portal which activates the host. Please note that the issue is intermittent. The function does work fine for a while.

On a parallel note, since the isolated process deployment, on some of the functions we have noticed "A collision for Host ID '**functionsv4placeholdertemplatesi**' was detected in the configured storage account. For more information, see https://aka.ms/functions-hostid-collision.".

#### Investigative information

- Timestamp: 2023-08-06 23:15:05.386
- Function App version: ~4
- Invocation ID: 85f949b2-2565-4e3a-b964-6ee9737cd186
- Region: Australia East

#### Error details

Description : A host error has occurred during startup operation 'f228ae71-6bab-43db-9603-a6844fa77dab'.
Last offline at 8/6/2023 10:59:28 PM
`Microsoft.Azure.WebJobs.Script.HostInitializationException : Did not find functions with language [dotnet-isolated].
at Microsoft.Azure.WebJobs.Script.Utility.VerifyFunctionsMatchSpecifiedLanguage(IEnumerable`1 functions,String workerRuntime,Boolean isPlaceholderMode,Boolean isHttpWorker,CancellationToken cancellationToken) at /_/src/WebJobs.Script/Utility.cs : 627
at async Microsoft.Azure.WebJobs.Script.ScriptHost.GetFunctionDescriptorsAsync(IEnumerable`1 functions,IEnumerable`1 descriptorProviders,String workerRuntime,CancellationToken cancellationToken) at /_/src/WebJobs.Script/Host/ScriptHost.cs : 746
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.Azure.WebJobs.Script.ScriptHost.InitializeFunctionDescriptorsAsync(IEnumerable`1 functionMetadata,String workerRuntime,CancellationToken cancellationToken) at /_/src/WebJobs.Script/Host/ScriptHost.cs : 520
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.Azure.WebJobs.Script.ScriptHost.InitializeAsync(CancellationToken cancellationToken) at /_/src/WebJobs.Script/Host/ScriptHost.cs : 314
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.Azure.WebJobs.Script.ScriptHost.StartAsyncCore(CancellationToken cancellationToken) at /_/src/WebJobs.Script/Host/ScriptHost.cs : 256
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.Extensions.Hosting.Internal.Host.StartAsync(CancellationToken cancellationToken)
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at async Microsoft.Azure.WebJobs.Script.WebHost.WebJobsScriptHostService.UnsynchronizedStartHostAsync(ScriptHostStartupOperation activeOperation,Int32 attemptCount,JobHostStartupMode startupMode) at /_/src/WebJobs.Script.WebHost/WebJobsScriptHostService.cs : 328`

#### Known workarounds
None. If the host is down, navigate to the azure function page in Azure portal and host will be active again

#### Related information

* Programming language - C#
* .NET version - 6.0
* Note : The functions are hosted in consumption plan. The app service plan hosts about 38 apps and they do use a shared storage account. However, each of these functions have unique host ids.

Start with VerifyFunctionsMatchSpecifiedLanguage in src/WebJobs.Script/Utility.cs, then follow the startup calls shown through ScriptHost.cs and WebJobsScriptHostService.cs. Compare the intermittent dotnet-isolated startup failure with the reported Host ID collision and production subscription details. Done means the failure is reproduced or explained and the relevant behavior has a verified fix or diagnostic.

Written by the indexing model from the issue text.