I am having this same issue. FLEX appears when triggering Performance Switch via cc #n, but it remains engaged. I could send it a note on/off message, but I'm afraid I don't know the cc to note on/off values. I did find this, though. The conversions listed here did not translate (that is, I used C4 or cc 49 to attempt to send Performance Switch a message. No response).
C0,1: C#0,2: D0,3: Eb0,4: E0,5: F0,6: F#0,7: G0,8: G#0,9: A0,10: Bb0,11: B0,12: C1,13: C#1,14: D1,15: Eb1,16: E1,17: F1,18: F#1,19: G1,20: G#1,21: A1,22: Bb1,23: B1,24: C2,25: C#2,26: D2,27: Eb2,28: E2,29: F2,30: F#2,31: G2,32: G#2,33: A2,34: Bb2,35: B2,36: C3,37: C#3,38: D3,39: Eb3,40: E3,41: F3,42: F#3,43: G3,44: G#3,45: A3,46: Bb3,47: B3,48: C4,49: C#4,50: D4,51: Eb4,52: E4,53: F4,54: F#4,55: G4,56: G#4,57: A4,58: Bb4,59: B4,60: C5,61: C#5,62: D5,63: Eb5,64: E5,65: F5,66: F#5,67: G5,68: G#5,69: A5,70: Bb5,71: B5,72: C6,73: C#6,74: D6,75: Eb6,76: E6,77: F6,78: F#6,79: G6,80: G#6,81: A6,82: Bb6,83: B6,84: C7,85: C#7,86: D7,87: Eb7,88: E7,89: F7,90: F#7,91: G7,92: G#7,93: A7,94: Bb7,95: B7,96: C8,97: C#8,98: D8,99: Eb8,100: E8,101: F8,102: F#8,103: G8,104: G#8,105: A8,106: Bb8,107: B8,108: C9,109: C#9,110: D9,111: Eb9,112: E9,113: F9,114: F#9,115: G9,116: G#9,117: A9,118: Bb9,119: B9,120: C10,121: C#10,122: D10,123: Eb10,124: E10,125: F10,126: F#10,127: G10
