Windows Live Writer and Blogger NotFound: Not Found error

Yesterday a problem started with Windows Live Writer and Blogger making it impossible to post blog posts or open published posts on Google's Blogger. I use the latest build of Microsoft's Windows Live Writer 2012. (Build 16.4.3528.331)
The first error showing says "Blogger returned the following error: NotFound: Not Found

 

Then the Sign in dialog box shows and clicking on OK shows the above message again.

The WLW log file shows the following:
WindowsLiveWriter,1.27804,None,00031,27-May-2015 09:52:23.884,"WindowsLive.Writer.Extensibility.BlogClient.BlogClientAuthenticationException: Account Login Failed - Please check your user name and password.
NotFound - Not Found
   at WindowsLive.Writer.BlogClient.Clients.GDataCredentials.EnsureLoggedIn(String username, String password, String service, Boolean showUi, String uri)",""

Not sure yet if this is an intentional change of the Blogger API or not. Hopefully Microsoft or Google fixes this issue soon.

Apparently this issue happens with other apps that are using the Blogger API too. Even Word 2016 Preview for Windows is not working with Blogger.

In the meantime a workaround that can be used is to create the post in Windows Live Writer and copy and paste to the Compose mode in Blogger, alternatively and sometimes the best option is to switch to Source in Windows Live Writer, select all, copy and paste to the HTML mode in Blogger. Note that this will not work if you normally upload images through Windows Live Writer. In this case you need to re-insert the images in Blogger. But if you have the images already online it is a decent workaround.

---

Update: Hopefully a solution is coming soon. This is a comment on the Blogger forum:
Hi everyone,
Thank you all for reporting this issue. The Blogger team is now working to fix it as soon as possible.
We will post an update here, once everything is back to normal.
Thanks and sorry for any inconvenience caused.
Blogger Team
---

New update that does not sounds promising: We appreciate you coming here and letting us know about this issue. It looks like this error is a result of an authentication problem between Google and Live Writer. A long time ago, we announced we were deprecating our old authentication system and we encouraged developers to move to the new one (OAuth 2.0). It seems that Live Writer is still using our old system, which is causing the issue. We are currently looking into it, but we suggest that users also reach out to Microsoft to report the issue.

Thanks,

Blogger Suport Team

p.s. please disconsider the previous official announcement.
---
Latest update from Google:

Hello again everyone,

We just want to let you know that we are working in partnership with Microsoft to come up with a quick resolution for the issue with Windows Live Writer and Blogger. We will provide you with more information as soon as we have it.

Thanks,

Blogger Support Team

---

Update June 2: Today it works again to post blogs from Windows Live Writer to Blogger. Thanks Google and Microsoft for working together on this.