Could your Fiber provider be blocking access to Google DNS?? Google this.. There are many reports of that happening. According to this thread it appears that the C-5 hub explicitly uses Google DNS.
When you open portal.hubitat.com on your laptop, that domain name is resolving using your ISP DNS. However, if the hub is hardcoded to use Google DNS, and your ISP is blocking, that would explain why the hub is failing to register, even though both have a valid internet connection.
