The other usual suspects are attempting to connect using a VPN, or proxy settings: System Preferences > Network > Advanced > Proxies. Confirm that none are selected. Next, check your router for firmware updates. Try restarting it. If in doubt connect your Mac directly to your cable modem (assuming that's what you use).
Also, please review the recommendations in If Safari doesn't load a page or webpage items are missing - Apple Support.
Lastly, contact Netflix. They have had continual (though unrelated) problems with Safari and their stated position to me was that it's something Apple has to fix. That's simply not going to happen. If that's correct, Netflix has been waiting several years. Several more aren't going to make a difference. To resolve that uncertainty try Firefox.