Pro Tools LE 8.0.5 Rewire FL Studio 12 (64bit)

[4thVisioN]

Hi, an old school PT user, new to this forum and Rewire.

So I've been trying to rewire FL Studio 12 (FL12) as a plugin on my instrument track and whenever I switch screens to play or hit a key in my FL12 with my Akai MPK25 which is hooked up to my PC via USB, it won't do anything. I go to my MIDI settings in FL12 and it tells me that "The specified device is already in use. Wait till its free and try again".
(I can play sounds in FL12 by using my mouse and clicking on keys and see that Pro Tools is recognizing it, so I'm guessing the rewire itself has been successfully done. The only problem I have is when using my MPK25 to do the same)

I can also play any other RTAS plugin instrument on my PT using the MPK25.
I can also use my MPK25 as a MIDI controller / keyboard without any issues when FL12 is run alone.

I've contacted the FL Studio support team and they've attempted to do the same with Pro Tools HD, and ran into similar problems. (it worked the first time but didn't the second time or something)

They pointed out that it could be a 64bit issue, but as far as I know, PT LE 8.0.5 and FL12 both support 64bit machines.

Maybe I'm missing the most simple MIDI settings, but can someone guide me through the steps to make this happen?

I also have a Digidesign 003 rack which is hooked up to my PC via Firewire and it's working perfectly fine as an audio interface for both programs.

Your support would be highly appreciated.