<strong>Left & Right Joy Con Sensor Rail With Flex Cable for Nintendo Switch OLED</strong>
These rails are located on the side of the Switch OLED console itself, not on the joy con.
The rails allow you to slide the controllers onto the console to dock and charge.
If the console won't detect a joy con or won't charge a joy con when slotted into the console, it's possible the console's rail itself has been damaged or failed.
Typically these will be physically damaged from a drop.