You're not using a satellite provider like Excede are you? Using the TOR browser in such a case usually fixes that. They've been known to cause issues to navigate to redfox domain URLs. Other than that i's highly unlikely that your ISP blocks a single URL. They can't even directly block access to the 8250 release (unless they know the exact path) because there's no physical link to it on the website. There's only the
https://www.redfox.bz/download/SetupAnyDVD.exe URL which is a static redirect to the always link to the latest release. If there was a new release for example to 8260, that link doesn't change, yet it will deliver 8260 exe to the user.
That said, the most likely reason is AV solutions blocking access, it that case telling the av to "shut up and behave" usually fixes that.