Sorry about this issue. It's been a while since this plugin has been tested against an older version of After Effects. What is the resolution of your composition/layer in this case? It might work on smaller composition/layer sizes in the case that this is just a memory-allocation issue. This effect is very memory hungry on the GPU in particular and others have run into issues in relation to that. Otherwise it might just be a compatibility with older versions of After Effects that I need to look into.
It only has a Vulkan implementation actually! So if it works at all then it is certainly using Vulkan. The memory costs and performance is very dependent on the resolution of the input frame, the more powerful the GPU the better the performance. Otherwise, it will be pretty slow... It will have to do a lot of redundant non-sharable work each frame at the moment until I can dial in on some optimizations unfortunately. For example, with still images there is a chance that work can be shared and re-used between frames in parallel. Though, for video-footage where each frame is basically a completely unique image, it will have to uniquely seam-carve each and every frame, which is pretty hard to avoid at the moment.