Video clips for iMovie not downloading; won't allow me to export movie

I have just edited a series of videos on iMovie (on my iPhone XR) that I need to upload to my Youtube channel. All of the videos that I used are saved on my phone in my photos. However, when I try to export them, I get a pop up that says that some of the videos are downloading from iCloud. Usually when this happens to me, the clips will start automatically downloading, and it will show me a little white timer for each clip so that I can see how long the downloading will take. However, for these videos, there is no little white timer. Instead, the thumbnails of the "downloading" clips are partially grey. While the pop up says the videos are downloading, there's no indication that they are, and even after waiting a while they never download. I have tried being on and off Wifi, and even tried turning off optimization of my iCloud photos. Nothing seems to work. I really need to upload these videos; if someone knows how to solve this problem, it would be a huge help!