I am trying to create an assignment for my students to receive their own individual copies of a Google Jamboard. I have followed all of the directed steps: chose External Tools as the submission type; selected Find and chose Google Docs Cloud Assignment in the configuration dialog window. However, instead of directing me to my Google Drive to locate the file, it defaults back to the dialog window with the message "An external tool can't be saved without a URL." So I've copied the link to the Jamboard I want to upload, pasted it under URL, and clicked Load in a New Window, but when I press the Select button, nothing happens. I've tried several times to no avail. Very frustrating. Can you help?