In the Editor app, I was unable to add new images to the file, using URLs in the Insert Image dialog box (Insert Image > URL > Confirm). When using the Image as base 64 option, images inserted successfully.
Thanks for the inquiry. We have logged this problem in our issue tracking system. The ID of this issue is AAPPS-59. Our product team will look into the details of this problem and we will keep you updated on the status of correction.
Could you, please, attach your document in zip file, the url of the image and the place, where you want to insert it?