Here is some part from active.log

18:30:17.019 [i]: VideoPlayer: mpv 0.33.0 /via 'mpvpipe'
18:30:17.569 [i]: Media: video 1920x1080 [PAR 1.000] at 23.976 fps
18:30:17.569 [i]: Media: codec type is AVC, YUV/4:2:0/10 bits
18:30:17.579 [i]: Playback: starting up...
18:30:17.610 [i]: Playback [c4c78d38]: Frame server (64-bit) C:\Users\REDACTED\AppData\Local\Programs\VapourSynth\core\vapoursynth.dll
18:30:17.614 [i]: Playback [c4c78d38]: deleted

I'm sure MPV is now working well with python and vapoursynth.
So what's the problem