Debug startup fails "no Functions runtime available"

It seems this is not a new issue, and you can find the old reported issue [here](https://github.com/Azure/azure-functions-host/issues/5145). I have tried all of the suggested solutions but no success.

In my case, I use v3-preview and .Net core 3.0. and I use FunctionsStartup to resolve DI.
It was working until this morning and it put me in a complicated position. why?

1. When I try to use PowerShell and try "C:\Users\...\AppData\Local\AzureFunctionsTools\Releases\3.0.3\cli\func.exe start"
I get
> No job functions found. Try making your job classes and methods public. If you're using binding extensions (e.g. Azure Storage, ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. builder.AddAzureStorage(), builder.AddServiceBus(), builder.AddTimers(), etc.).

`






`

2. I have built the whole of this solution with .Net Core 3.0 and Azure function v2 is not compatible with that at all. so I can not just create a V2. it takes more than the time that I have to rebuild all .net core 2.x

3. Azure Function V2, has this issue https://github.com/Azure/azure-functions-host/issues/4049,

Now, I need a proper answer. how should I fix my problem? Can I trust this v3-preview?
Until yesterday everything was fine.

Start by reviewing the linked issues 5145 and 4049, then inspect the reported func.exe startup command and the listed package versions. Compare the v3-preview and .NET Core 3.0 details with the reported “No job functions found” output. Done would require a confirmed cause and actionable compatibility guidance, but the issue does not identify a code or test change.

Written by the indexing model from the issue text.