Do you have an audio output connected? Like, speakers, headphones, etc? RO is finicky like that. If you have the sound output enabled in the Setup.exe file in your RO folder (which it is by default) you NEED to have an audio output, else your client can't open.
Oh, you also don't need to KEEP the headphones plugged in by any means. As soon as the client opens, you can unplug them and it will be fine.
I think you just need an audio and video driver. I never had speakers or headphones in my Desktop, and I play sometimes at it, but I have audio drivers, and always worked.
Characters: Magnus Elwyn - Hunter Magnus Blackbeard - Rogue Magnus Crowley- Mage- Future Wizard High Septon- Acolyte- Future Priest Magnus Thorvaldsson- Merchant
I'll bump, I may have the solution.
Now, I got this problem too, if I open the game by the patch, sometimes the client just won't open. Try the other clients (heRO_green, etc), worked for me
Characters: Magnus Elwyn - Hunter Magnus Blackbeard - Rogue Magnus Crowley- Mage- Future Wizard High Septon- Acolyte- Future Priest Magnus Thorvaldsson- Merchant