Try pressing Ctrl+F5 at the same time. Control+F5 forces a complete refresh of a web page. It clears the cache and downloads all contents of the page again. This endless looping is generally caused by an issue with cache and cookies. You can use Ctrl+Shift+Del to get to the settings page quickly to clear your cache and cookies. Close all browser windows and start over. You can also try a different browser. Chrome generally works best. You can also try signing in here first: https://live.altium.com/#signin Then navigate to the forum: https://forum.live.altium.com/ Try using an incognito window in Chrome, or a new private window in Firefox or Edge. To determine if this may be an issue with your AltiumLive account, try on a different computer and have someone else try it using their credentials on your computer. If it seems to be an AltiumLive account issue, try resetting your password. If that doesn't help, contact us so we can make sure your account is in the correct "spaces" and/or try resetting your account. This issue has also been known to be caused by blocked network traffic. You can try turning off your local firewall &/or ask your IT support to allow the addresses/ports through your network to the Internet that are listed in this Knowledge Base article: https://www.altium.com/documentation/knowledge-base/url-address-and-port-information
To test for a Network traffic issue, you could bring your computer (if portable) to a different internet connection (try it at home) or (if WiFi enabled) disconnect from your work network and connect to a cell phone that has been set up as a WiFi hotspot.