CSS conical gradient is still in the experimental stage and hasn’t been adopted yet by the majority of modern browsers. Only Google Chrome 69+ and Safari 12.1+ in desktop browsers and iOS Safari 12.2, Android 12.2+ and Chrome Android 67 among mobile browsers provide browser support for this feature. Other popular browsers like Mozilla Firefox, Opera and Edge still haven’t rolled out support for conical CSS gradient.
In order to provide CSS conical gradient functionality for unsupported browsers, you can make use of an ingenious polyfill by Lea Verou.