I've used Click Once to deploy a pair of applications for well over a decade without issue. Sometime last summer, date not particularly certain, something changed. One of the applications will not install on a new computer, and I haven't dared try the other one.

At first, I thought this might have been a signing issue, and was able to set it aside for a while as that was getting sorted out...or more specifically, my request to sort it out was being ignored, which worked well for a couple months until it didn't work well anymore. I don't really care about the signing on this, so I've been using the temporary certificate for signing the file for all this time. Occasionally, those have gone stale and needed to be replaced, so I thought I'd get a real certificate. Turns out, those are too expensive for something as trivial as this, so I tried a new temporary certificate and this failed as well.

The cause for the failure is a bit mysterious, and somewhat suggestive. I have not done any real study of this since last fall, and I didn't find much then, but the details of the failure mention an invalid username and password. There is no such set of credentials for this program, so that was a bit odd. However, I think I DO know what it's asking for.

I can install the program just fine so long as I am logged into the web server on the computer that I am installing the program onto. The program fails to install with a pretty useless error message on any computer that is NOT signed into the web server. The details talk about those missing credentials, and don't say anything else that looks useful to me, so I believe the credentials it is asking for is the credentials to sign in to the web server, something that should never be required for installing something.

I'll be studying this more over the next couple days, but I thought I'd toss that out there in case anybody knew why my ClickOnce deployment, which had been working fine for years, suddenly wants people to log into the web server to install?

I realize that this is a deficient question, but there's not all that much to go on. That message about the bad credentials is the only error being reported, and the fact that it works fine on computers logged into the web server, are basically the only pieces of data I have to go on, at this point. If anybody has any suggestions, I'd be interested in hearing them.