It’s pretty common issue that every Airpods user experience this issue of left airpods not working or right airpod not working and you need to reset Airpods to fix this issue and update software and pair and unpair and other methods to fix this issue and If your airpods are not working even after you have resetting then there are couple of simple methods and tricks that you can apply which will help you fix the issue.

If your left Airpods are not working even after reset then the first thing you need to check is whether your left airpod is properly charged or not and if it is lacking charging then left or right Airpods will not work after reset as well.
There’s No Sound On One AirPod

If there is no sound from the left or right airpod then check with charging and charge your airpod and change microphone and speaker settings and check audio and visual and balance sound by dragging slider to middle.
Left Airpod Not Working Even After Reset
Below simple troubleshooting methods will fix left Airpods not working after reset and after update issue.
Charge your Airpods Properly
You need to charge your airpods properly and if left airpods are not charged then airpods will not work. Remove the left airpod from the airpod charging case and charge properly and check charging of the airpods.
Clean Airpods Charging Case
If airpods charging case is filled with dust then when you put your airpods to charging case then it will not charge properly and you need to clean airpods charging case with fresh soft cloth and blow some air into airpods charging case and check if there is anything stuck or dust or debris filled in side airpods charging case.
Clear Ear Wax from Airpods
If left airpods are stuck with ear wax then left airpods will not work and this will prevent left airpods working properly even after you reset and you need to clean earwax from airpod using soft cloth and then check.
Software Update Issue
If there are any software related issues which are causing the problem with airpods then you need to update your iphone to the latest version and then check. Sometimes, bugs from Apple IOS can also cause this issue.
Hardware Issues
If there is any hardware related issue inside airpods then this issue of left airpod no sound or not working issue will occur and contacting apple support will fix the issue with left airpod no sound.
Contact Apple Support
If nothing works and still your left airpod is not working then you need to contact nearby apple support and ask them to check for damage or hardware issues with your airpods.