The auto-populate feature isn't working.

First, check that your files are named correctly. If there is an error in the naming, the auto-populate feature will not be able to recognize your files and will upload them to the assets panel. If you did not follow the auto-populate naming convention, your assets will load into the assets panel. If you attempted to use the auto-populate feature but there are mistakes, an error message will appear indicating you need to rename your files. If you correctly named all your files, a window will appear asking if you'd like to populate the canvas. 

Second, check that the dimensions of your assets are all 1080px by 1920px. Incorrect dimensions can also result in an uploading error.