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HTTP Error 503. The service is unavailable, until visual studio loads the project

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Posted on by goyalsachin6

Hi Experts,

I noticed that in my dev environment, I always get 503 error until I open a project under visual studio. Is it something related to IIS express which visual studio starts while loading the project. If yes, any solution which can fix this issue?

Note: The above issue is not related to services like IIS admin and the world wide web.

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Raj Borad 1,313 on at

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HTTP Error 503. The service is unavailable, until visual studio loads the project

I faced an Error after fully building my custom model.

I have also found a solution.

Open IIS as an administration, Under the application pool > Start the AOSService.

Hope it will work you.

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Andrew Huisman 313 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

André, thank you so much! We applied the latest deployable package from the Dev branch to my environment and now it works the way it should!

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André Arnaud de Cal... 297,611 Super User 2025 Season 2 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Hi Andrew,

I had the same issue last week on a demo machine which was also a DEV topology. We updated the machine with latest releases and removed one package. At that time, we had the same issue. After installing a new deployable package, the issue got resolved.

Can you tell what might be changed when you run into this issue or is this a fresh VM?

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Andrew Huisman 313 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Did you ever get this resolved? I have the exact same issue right now in my dev environment. Only works if VS is open.

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goyalsachin6 21 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Yes Ludwig.

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goyalsachin6 21 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Hi Sergei,

Yes, This issue comes when you start the VM and try to access the application. I believe it supposed to use IIS which I checked is started but still application remain unavailable. however when you open visual studio which eventually starts IIS express it becomes avaialable and after that when you close the visual studio, your application again become unavailable.

I also notice that in build/test box, application always remains available when you start the VM.

There should be some difference in terms of settings for both types of VM which is causing this issue.

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WillWU 22,359 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Hi goyalsachin6,

When you open Visual Studio, the VM switches to use IIS Express instead of IIS, which means that IIS will stop and IIS Express will start. This also means that you cannot start IIS again because IIS Express is now using the port.

When you close VS, it will close IIS Express and restart IIS for you.

And you could restart IIS Express by selecting Dynamics 365 > Restart IIS Express in Visual Studio.

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Sergei Minozhenko 23,093 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Hi Sachin,

Does it happen every time when you try to open a project or only when you just started VM? I noticed similar behavior but only after VM restart and looks like not all services are started at this point.

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Christoph Thaler 5,442 on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Hi Sachin Goyal,

if it is D365 I saw it in our environments in some rare cases in the past. In our cases it was related with IIS. Please check the AOS and application pool in IIS. If one of them is stopped the web site is not available.

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Sukrut Parab 71,699 Moderator on at

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RE: HTTP Error 503. The service is unavailable, until visual studio loads the project

Take a look at suggestions from the link below

community.dynamics.com/.../process-to-debug-not-found-and-503-whenever-trying-to-build-rebuild-or-debug

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