What is causing a 404 error in VS and 405 error in the browser while creating a local Provider-Hosted app (not azure hosted) for SharePoint Online?

Question

I am using Sharepoint Online and VS2019.

I was asked to create a Provider-Hosted App for SharePoint Online, where the App is hosted locally on a computer/server (without hosting on Azure).

As a test, I am trying to load the default Hello World Page that is auto-generated.

After Googling and watching YouTube videos to follow and understand some steps, I ended up using this guide (the closest guide I could find without mentioning hosting on Azure).

Now I completed the following:

1. Created a Developer Site in Sharepoint Site Collection Created a

2. Provider-Hosted MVC app for Sharepoint Online and using Windows Azure Access Control Service Created Self-Signed Certificate for default application pool.

3. Create a Https binding to default localhost.
4. Generated Client ID and Secret from Development site, then configured the App.

After deploying and starting the app, I noticed the messages followed by the error:

Clicking on OK loads the following page,the 405 error-

I am not really sure what I am doing wrong. Any assistance will be appreciated.

Answer 1

1.Try going to IIS and checking to make sure the App Pool you are using is started. A lot of times, you will produce an error that shuts down the app pool. You just need to right click and Start and you should be good to go.

2.Often, this error occurs because an error or configuration change has occurred that requires an update to your Application Pools, an IIS reset, or both. You can reset IIS by opening an elevated command prompt and typing iisreset.

For more information you can refer to the article below:

https://docs.microsoft.com/en-us/visualstudio/debugger/error-unable-to-start-debugging-on-the-web-server?view=vs-2019