Network errors usually come from one of five things: a busy CoGrader server, your internet connection, a school firewall, a file that's too large, or a browser extension. This article covers each one, then lists the domains your IT team should allow.
Common causes of network errors
1. Our servers are busy. At peak times you may see a temporary error. Wait a few minutes and try again.
2. Your internet connection. Make sure your connection is stable and active.
3. A firewall at your school or district. Firewall errors usually appear almost instantly, as soon as you click a button. Ask your IT team to allow the domains listed below.
4. A timeout. If the error appears after a long wait (usually over 100 seconds), the file may be too large. Make it smaller by compressing it or removing extra content. There's no hard limit, but files over 15 pages can cause problems.
5. Browser extensions. Some extensions interfere with the connection. Try turning them off, or open CoGrader in an incognito window. See also How to Hard Reload and Clear Your Cache.
How do I know if my network is the issue?
Is it only you, or everyone on the network? Check whether colleagues on the same school network see the same error.
Switch from school WiFi to a phone hotspot. If the error goes away on the hotspot, the school network settings are the likely cause.
Domains to allowlist
Your school admin will need to allowlist (whitelist) the following domains for you to use CoGrader:
Sign-in
For schools using Google sign-in, also allow:
accounts.google.com
apis.google.com
If these domains are blocked or restricted, users may be unable to log in with Google.
School platforms
If you connect CoGrader to Google Classroom, Canvas, Schoology, Blackboard or another platform, make sure that platform's domains are also allowed. The CoGrader browser extensions for Canvas, Schoology and Blackboard need CoGrader domains reachable from inside the LMS.
Security software in school networks
Many schools and universities use security software that filters or proxies web traffic. These systems can block CoGrader or its integrations. Common ones that may need adjusting:
[McAfee] McAfee Web Gateway
[Cisco, formerly OpenDNS] Cisco Umbrella
[Broadcom] Symantec Cloud Secure Web Gateway
[Palo Alto Networks] PAN-DB Private Cloud
[Zscaler] Zscaler Internet Access
[Sophos] Sophos Firewall Public Cloud
[Barracuda] Web Security Gateway
[Fortinet] Fortiguard URL Filtering Service
Make sure CoGrader's domains, and those of any connected platforms, are allowlisted in this software.
SSL errors
Messages like “Network configuration issue” or “Looks like [certificate] is the wrong SSL certificate” can appear if SSL inspection or decryption is turned on for the school network.
Fix: turn off SSL inspection/decryption for all public CoGrader domains.
If the problem continues, contact CoGrader Support and tell us which security software your network uses.
Common error codes
429: we're being rate limited by a provider. The message usually says which one.
500 unhealthy stream: we're being rate limited by Azure.
502, 503, 504: most likely a timeout.
auth/network-request-failed: a sign-in error, most likely caused by a firewall.
For other messages, see Understanding Error Messages in CoGrader and How to Fix Them.