So I was able to publish my wpf application using click once without any problem for a couple of months. But yesterday when I tried I got an odd looking message.
When choosing Yes option the publish stops and fills error list with those errors:
I tried searching online but without any success.
I resolved this issue by unchecking the passive mode check box when prompted for the ftp credentials
This issue started happening to me after I upgraded to Visual Studio 2019 16.7.3. I also updated my application from .NET Framework 4.7.2 to 4.8. (Although I doubt that's the issue, I did not revert to 4.7.2 to test it.)
My solution was to publish to a local folder and then upload those files with a separate FTP application (e.g., FileZilla). Upgrading my existing ClickOnce app worked fine.
Details: In your application's Properties page, select the Publish tab. Change the Publishing Folder Location field from "ftp://whatever" to "C:\publish-MyApp." Click the Publish Now button. VS will create the files pretty quickly. Next, use your FTP application to upload the contents of the C:\publish-MyApp folder to the existing installation folder on your server. This overwrites the existing setup.exe and MyApp.application files and adds a new folder (e.g., MyApp_1.2.3.4) in the Application Files folder.
(One side benefit of this method is that it's faster to publish because FileZilla is a lot faster at uploading than Visual Studio.)
