I also had this issue a while back in which StudioOne states "Video failed to write". The solution I found was this. On the export video page, on the top left, where it says location, click on the 3 dots to the right of the directory box. This should open a new window from your computer showing you your songs location. Within your folder it has opened for you, you have to make the folder for "Video" yourself. This has been a bug for awhile in which S1 is not creating the folder in which the video is supposed to export to. Maybe one day they will fix this bug but until then, this has been the solution that has worked for me. Best of luck!