Just like the topic said, it's crashing on startup. When I try to open it, an incomplete version of the UI appears for about 10 seconds before it just completely dies. I tried the uninstall thing from the FAQ on 4.5 and it didn't work, and I'm about to try it again on 4.6, but my expectations aren't very high. Running Windows 10 with a RX 590 (with up-to-date drivers) and Ryzen 2600X.
Something that I noticed is that 2 instances of action_svc.exe open whenever I try to open Action!, and they stick around indefinitely after the crash.