salam my friend do you have k-lite codeck installed if not pls install them and when finished go for codec tweak tool choose preferred decoders and change all for lav it will fix video not encoding and also avisynth filters selection reply if all things are good
what i mean is the the output file dosen't have encoding settings
x264 with no parameters
lots of thing that would help
opencland cudaa
encoding mkv to mp4
new x265
new x265