SSL Certificate Error when connecting to https://canvas.agu.edu.tr/

Sentry error here: https://sentry.io/organizations/hypothesis/issues/1242705344/?project=259908&query=is%3Aunresolved&statsPeriod=14d

User gets the "Something went wrong" page when they try to open a Canvas assignment in a new window. We're not able to validate their SSL certificate/ We can open canvas.agu.edu.tr in Chrome and Safari, but not in Firefox. We use https://certifi.io/, the same as Firefox.