I am also having this issue, I tired moving it to a different location, but it seems to be cycling through a few errors, but it always has this.
Something went wrong
itch-setup, v1.18.0, built on Apr 10 2019 @ 07:29:17, ref 57838bc373361f2c8938336674247f869999e862
HTTP file not found on server
htfs.Open (initial request)
while opening remote signature file
Error during warm-up