When using Vegas Movie Studio 15, I had no problems using files from various sources. Since upgrading to 17, I keep on getting a rejection response of "invalid format". My own personally done video clips, as well as ones I've gotten from Storyblocks, still work fine on 17. But what I got from Depositphotos---which previously worked on 15----does not work on 17. What can be done to fix the problem??