Probably your video is a HEVC format the new format for video and photo is a HEIC format. To view the video you must install the special codec from Microsoft web site this is free and you need the last updated Windows 10 version. The other sokution is to transform the HEVC video in a MP4 video H.264.
We need more information - cryptic answers are not good for helping you solve the issue.
Please read this topic and come back with the specification of your computer and the full name and version numberof the program you are referring to, as requested by @browj2, details of how to find this are in the linked to topic.
Also provide a MediaInfo analysis of one of the iPhone video clips - again details are in the linked to topic the MediaInfo analysis will tell us what is missing from the program. .