Whatsapp has limitations on how big a file you can send and it actually trims down and recompresses the video to fit a certain limit. If it still cannot make it fit into that limit, then it will reject the video file automatically. There’s no way to change this as this is a server-side ‘imposition’.
If you want to share a large file I’d suggest you upload it to a Cloud service and then share the link. You can use Google Drive, Dropbox, etc.
Source: androidcentral [how to get whatsApp to accept large video file]
