I'm on a fresh install.
At first, when I was trying to install an app from the app center it would say 'starting' with an empty loading bar that would remain empty forever.
After looking up some solutions I tried running
sudo apt update and
sudo apt upgrade,
now when I try to install an app the behavior is essentially identical except it now says 'Waiting' instead of 'starting'.
EDIT: the problem no longer exists for me on 0.4.1 with the new App Center.