I got an answer from Mirillis support. My problem was "Thank you for your diagnostic report. This issue is related to your AverMedia hardware and streaming engine that is used in Rec Central. Uninstalling this application should fix your launch issue." I unninstalled avermedia and after it worked. :D

I have same problem. Reinstalled windows and nothing changed. Hey, I have a problem! I can´t use my Mirillis Action it´s start but than it´s close!I can´t see a window nothing! Here a video from the problem. https://www.youtube.com/watch?v=sJZtxj0lQLI My pc: Windows 7 AMD FX 6300 MSI GTX 750Ti 2GB 8...

If u make it to can use avermedia extremecap u3 capture card will be nice

Action don't work 100% on win8.

go control panel/System and Security/Windows Firewall and click Allow a Program or feature through Windows Firewall then click on Change settings and click on Allow another program, select Action! click add and then ok.
After ure doing this u can upload this with Mirillis action
Have fun.