Not that I have anything against offline installers, as I download these and use them not infrequently, but one has to realize that servers for the installers that do "on demand" downloading do go offline occasionally. Sometimes it's for scheduled maintenance and sometimes it's not. But, generally, if you try again later things will work just fine after those servers are online again.
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Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363
Tolerance is the positive and cordial effort to understand another's beliefs, practices, and habits without necessarily sharing or accepting them.
~ Joshua Liebman