A variety of networking issues can cause a bad gateway error, such as issues with the internet service provider (ISP), router problems, or DNS malfunctions.
Try reaching out to your IT as this is an internal issue.
Your IT can try the following solutions:
Refresh the Page.
Clear Browser Cache.
Try in Incognito Mode.
Flush DNS Servers.
Test on Another Device.
Check Error Log.
Check Plugins and Themes.
Check CDNs.