Same problem with large size video clips in my Creative Cloud account. I'm using Premiere Clip on an iPad Air. I was able to import three files 174 MB, 3.7 MB, and 2.8 MB into a timeline. I was NOT able to import two files 1.45 GB and 817 MB. For the two large files I see the grey spinning icon in the timeline for a while and then it just goes away or Premiere Clip just crashes. The iPad has plenty of space available. The other three smaller files appear in the timeline after importing them from Creative Cloud. I can even preview the large movies before clicking open file. I've tried a restart of the app as well as a reboot of the iPad.