NVIDIA provides two types of hardware acceleration technologies - NVCUVENC for older videocards and driver versions and NVENC for the newer graphic cards and driver versions.
NVCUVENC technology is supported in driver revisions up to 337.88.
NVENC technology is supported in driver revisions from 340.52.
Movavi Video Converter 15 does not support NVENC, only NVCUVENC. The same applies to the older versions of converter.
Movavi Video Converter 16, Movavi Video Editor 12 and Movavi Screen Capture 8 and later do not support NVCUVENC, only NVENC.
The same applies to the newer versions of converter/editor/screen recorder.
To enable NVIDIA hardware acceleration in the earlier versions of Movavi products, you may try installing 337.88 driver for your graphic card.
To enable NVIDIA hardware acceleration in the newer versions of converter/editor/screen recorder, try installing the latest available driver for your videocard.
If you are not sure whether the accelerations are available for your card, please refer to this table: