Network error-There was a network error while loading the document

I’m an online teacher. Some of our students submit work via Kami. Everything was working fine, until about a month ago and now about half of the work turned in I get “there was a network error while loading the document”
Why is this happening? How do we fix it? Any help?

![Screenshot 2020-12-23 at 8.49.22 AM|569x277]
(upload://9A9Onxp8ZvUDlrICY0xWVxkaahd.png)