Premier Rush and problems loading MP4 files.

My Go Pro 10 outputs MP4 video. Until recently the Rush editor worked fine. Recently it has been unable to load the video files due to a missing Codec. I have Rush installed on 2 computers. The desktop windows 10 refused to load the MP4 files. I tried installing different versions of Rush to no avail. Winows 10 does not have the particular CODEC required but even so the programn has worked in the past. In desperation I tried the laptop windows 10 with all the same  settings etc. The file loaded perfectly. With a creative cloud membersip, The Photography Plan Premier Rush is supposed to have the required Codec installed. Recently both computers keep receiving warning messages about my outdated Video adapter. The laptop is a Windows Surface Book with two Video adapters one in the base and the other in the screen. I have no idea what the problem is, except it is possible that on starting Premier Rush it configures itself with various settings. Maybe in the case of the desktop it is not loading the required Codec. Justin Goodwin