I also had trouble with the EpicInstaller (multiple times) for UE4.19 on my Win10 machine

In my case, when launching the .msi, the install screen would appear, I could change target dir if I liked, etc… but, when I clicked on the Install button, it immediately complained there was something wrong and that the Installer ended prematurely. Digging into the log file it mentioned at the end code 1603. After chasing all the possible solution options found on this support forum and others, unfortunately found none to solve my case. I had a thought to try installing under “Safe mode” (clever, right?), however it complained that, “the Windows Installer Service was unavailable in Safe mode”…figures, but got me thinking… Once back up in normal mode, I checked the services. Lo and behold, my Windows Installer Service was set to “Manual”. I started the service and boom, the .msi worked with no issues. So, I offer this as another possible option, to add to the list to try, if anyone running Windows is having trouble with their installer.msi’s.
Cheers, g.