Left AirPod stopped working?

Went to use my AirPods two days ago and the left one never made the noise to clarify it’s connected, continued to play music and was only getting sound from the right one. They were fine the previous night and I have charged both them. I tried ‘forget this device’, resetting them then reconnecting my AirPods to my phone but it’s made no difference. Two days later and the left AirPod is still failing to work. Very worried and would like some help!