You can verify if UltraPix is actually used during playback/editing by utilizing Adobe Premiere on-screen debug information.

Use the keyboard shortcut “Ctrl + Shift + F11”. Afterwards, click stop&play button to restart video playback. Now you should see a text overlay over the video window. The last row named “PF” should show “CmptoMXFJ2KImport” which means Adobe uses UltraPix Importer.

If you do not see it, you may try to reinstall UltraPix, also make sure you use a standard version of JPEG2000 video. Despite the fact that UltraPix makes 4K/8K editing possible on a mainstream class hardware, there still is a recommended minimum configuration for CPU/GPU.