People were understandably ticked off when they found out that their shiny OnePlus phones cant stream in HD. Both the OnePlus 5 and OnePlus 5T were stuck streaming SD content because they lacked the necessary certifications. The company now has a program in place to resolve that, but you may not like what you have to do.
The Widevine L1 certification that is required by the major streaming services for HD video needs to be installed over a physical connection with an authenticated PC. This means theres no way to do it over the air.
You have to send your phone back to OnePlus and you can expect it back in no more than 5 working days. The company will cover the courier costs in its service regions North America, Europe, India and China. Users elsewhere will have to pay for shipping themselves.