hmmm... I don't have any problem downloading the installer app from the App Store!
What happens when you try that? Maybe it is your location? Where do you live (what country?)
Madison, WI
I haven't tried re-downloading and re-making the installer yet. (The need to do so would suggest my installer could somehow be altered? I suppose the USB drive could be experiencing corruption... that doesn't give me any other weirdness or error... seems like a stretch.) I'll try that anyway in a bit today when I get back to this project.
I downloaded the full installer with the help of the High Sierra Patcher Tool from:
http://dosdude1.com/highsierra/
I created two different patched installers. One with the dosdude1 script (only works on some models) and one manually (covers the rest). Manual patch was this:
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled
Browse to Contents/SharedSupport/ and delete the file named InstallInfo.plist
Instructions to run either patched installer start with this:
Connect to internet.
ntpdate -u time.apple.com
All was happiness and light. One or the other worked depending on the model.
re: the "Masochism" comment. This isn't me choosing to run the installer with the multi step thing. It's how it's written to work by Apple. And it's actually a convenience to get an up to date install in more or less one step. When you can actually connect to the Apple server anyway...
I also had a machine running 10.13.3 that I connected to the app store to download an update for it that way (normal SOP). It would download the latest iTunes but not the 10.13.4 revision. It went through the motions but the part where it restarts to the installer screen (apple with remaining time text under it) just paused a moment and the machine quietly restarted with 10.13.3 revision still current. Repeated this to verify the pattern too.
Their server is saying "try later" with using the installer and just quietly skipping the .4 revision with the SOP update.
If I'm being stupid here somehow (always a risk of that), I don't see where yet. I really haven't changed anything. If this is Apple detecting me downloading an update too many times and blocking me or some such... that seems like a stretch too. Looks for all the world like they realized the bug with their errant default selection of Filevault enabled in the installer startup script and it bricking people's 10.13 install after the .4 update and just shut their server down until they could release a fixed update. I can only speculate.
I'll have to try downloading again and then hacking around if nothing has changed. I know just enough about what I'm doing to be dangerous... It should be technically possible to coax this installer into at least a 10.13.1 install with no Apple server connection though.