I am running REAPER as a host and tried to use FL Studio 12 (both x64) as a VSti and ReWire slave. Can't get it to work in either case. The respective error messages I get are "Failed to open audio engine . Another instance may already be running. If not, try to reset FL settings" when I try to run FL Studio as a Rewire slave and "The FL engine couldn't be linked, probably because another instance of it already running or because it hasn't been installed properly." I googled these errors and set all the application to Run as Administrator, checked my Task Manager to see if FL Studio was actually running in the background or not (it was not) and even tried re installing FL Studio 12. Nothing helped.

I tried running Ableton Live 9 in REAPER and it works fine. I hope this is not hardware related (I am using a Focusrite Scarlett 2i2 interface, if that's helpful). Please help I really wanna use FL Studio's piano roll and MIDI editing capabilities(plus some of the synths like Sakura and Sawer).

Thanks in advance.

 

I'm not using FL studio, but check if there is a option in FL studio like "use as rewire" like in Reaper/Live etc...
Also try to add FL rewire first on Reaper track, then run FL studio. Maybe help.

 

Hope this video will load for you(for some reason for me doesn't want to load if i forward video beyond 34 min):

http://www.ustream.tv/recorded/6891224

And this: http://forum.cockos.com/showthread.php?t=62371