Sometimes Iris recognition do not work properly in Samsung Galaxy S8+?
Please check you attach unofficial screen protectors (privacy protection films, tempered glass protectors, etc.) to your device. Keep in mind do not cover the proximity/light sensor area with screen accessories, such as a screen protector or stickers. Doing so may cause the sensor to malfunction and the iris recognition LED may not turn off even when you are very close to it. Additionally, dirt and debris on the iris camera, LED sensor, or proximity sensor may cause the device to have difficulty recognizing your irises.