I have a set of assignments that use the external tool function to link to resources from the textbook website. These tools all worked a week ago. Today, I started getting an error message saying "couldn't find valid settings for this link" and the site returned me to my home page. When I entered the Edit function of an assignment to check the settings, nothing was out of the ordinary. I copied and pasted the URL for the external tool into a different tab to make sure it wasn't the textbook site - the site loaded properly.
I use a Macbook. I have tested this out in Firefox (including a private window), Chrome, and Safari, both in my view and in Student View. I have restarted the computer to get a fresh start; also no luck.
Anyone have any ideas?