Helix searching user by username returns 401 error

[BarryCarlyon]

Requiring OAuth for Helix Twitch API Endpoints

In an effort to standardize authentication and provide security improvements for the Twitch community, OAuth will soon be required for all Twitch API endpoints in the new Twitch API, also known as “Helix.” The goal of this announcement is to provide a timeline, full details of this new requirement, and answer a few anticipated questions. Please feel free to add further questions via the comments below and we appreciate your feedback during this process. Update (2020/06/02): See “How will this …

The change was permanent on the 11th

All helix endpoints now require an oAuth token to be present