Hi, only Arturia Support knows, if there are issues with FL12. I personally don't own FL12, I use Studio One V3 and after a few struggles it's nearly working there (Spark VST with SparkLE).
So did you open a ticket for Arturia Support help?
Here in this forum you just get a lot of views, but nearly no answer, so Arturia Support adresses better, they answer in a shorter time, than here...