I got a Arris SBG8300 recently and ever since I have been unable to access some websites and mobile apps (like What’sApp) on ethernet and wifi. Some websites are just ridiculously slow. Speedtest.net does not even work. I cannot sync my clock in Windows to any time servers (tried microsoft, google, ntp.org, nist.gov).
My ISP says there’s nothing wrong with my connection. I’ve tried updating DNS servers and still having the problem.
When I switch to my sibling’s wifi (same isp, different modem) all of these things work instantly and quickly.
Not sure what else to do or what to check.