Answer
One genuinely actionable diagnostic direction, though not a guaranteed fix: check for security software running on the APPLICATION SERVER itself, such as antivirus, a firewall, or an application-performance-monitoring agent, that might be blocking, quarantining, or otherwise altering .NET-related files (like a required .htm manifest-adjacent file) as they're served to the ClickOnce client. A computed-hash mismatch like this commonly stems from a file being altered or blocked in transit by exactly this kind of security tooling running on the server side, rather than genuine corruption of the deployed files themselves — reviewing what monitoring/security software is active on the machine where IFS Home is installed, and whether it's restricting these specific file types, is worth checking even after the more standard reinstall/reconfigure/cache-clearing steps have already failed.