Problem with Twixtor in FCPX

Hi... I have been looking to buy Twixtor on FCPX but I am hearing of some issues when used in FCPX.

Someone I know who uses it mentioned they are having problems as even though they have a licence they get the Yellow X registration screen which flickers on and off. As such they can only use it in FCP at the moment.
They tried reinstalling and select the install GUI licence option after putting in their registration info but the problem still persists.

I just wanted to know (before I invest a chunk of my own cash) if anyone else is having issues.
I need the plug in for some slomo work and if its going to be a problem I'll save the money and make do with FCP's Optical flow even though it's not as good based on the trial I have been testing.

Anyone else seeing issues ?