Connection issues on Windows 7



I’m trying to connect my Muse headband 2014 on my windows 7 computer (with my computer bluetooth, not a dongle). I paired it with my computer, then when I want to launch muse-io, Connection failure appear, even if I add the com-num/name.
The problem is that it already works yesterday, but today the connection failed.

I tried :
- remove Muse from my bluetooth devices of my computer and paired it again
- try with the Muse headband directly after pairing, or in pairing mode after pairing.
- I reboot my computer and the Muse headband
I don’t understand why it worked yesterday but not today.

Do I have to buy a dongle or can I do something ? (the bluetooth version of my computer is bluetooth 4.0)