I had a previous version of Twixtor running (I believe Twixtor 6.1). I purchased Twixtor 6.2.1. and installed with serial for AE and Pr (CC 2015). The watermarks disappeared in my timeline, convincing me that the process was successful. The direct Premiere export works as well - no watermark. However, when I export with media encoder CC 2015, the watermarks come back.