I found that the launcher does not like to execute the client in Windows10 if you don't have it set to "run as administrator" - even with UAC "off" - presumably because it is installed in the default location on C drive. (Voice attack suffers from this too.)
This can often help. Even though the OP is has
an Admin account, it's not
the Admin account (which is different) so using "Run as Administrator" can certainly help. Why it used to work and doesn't now is a mystery, though sometimes even the most innocent looking Windows Updates can cause weird stuff to happen.
Note: it's really not a good idea to install games and the like in the default C drive location. I
never do this, yet time and time again I read where people have problems when they've done so. I've always partitioned or used another physical drive entirely for games and I don't get issues like this.
Note 2: I might be remembering wrong, but if you want to change the install location of ED, can you not still just
copy the build to the new location, install the new Client pointing at said location and it'll recognise the existing files and
not re-download them? I did this when I migrated my build to a new machine as I was on a really slow connection. Note: this is for the ED Launcher version, not Steam, though it does of course work for Steam titles too.
Scoob.