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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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Ludwig Reinhard Microsoft Employee on at

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Hi Sachin,

Is this related to D365FO?

Best regards,

Ludwig

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Sukrut Parab 71,710 Moderator on at

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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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Christoph Thaler 5,442 on at

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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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Sergei Minozhenko 23,093 on at

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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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WillWU 22,361 on at

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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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goyalsachin6 21 on at

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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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goyalsachin6 21 on at

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Yes Ludwig.

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Andrew Huisman 313 on at

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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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André Arnaud de Cal... 300,731 Super User 2025 Season 2 on at

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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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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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