Problem
Troubleshooting for headphone jack not working on robot
Solution
There are multiple types of headphone jacks, note that the RoboKind R25 robots are supported with the MONO option shown below.
If headphones with a mono jack are not available, it is possible to purchase an adapter, for example https://www.amazon.com/Ancable-Extension-Receiver-Extender-Repeater/dp/B075SV6XZY/ref=sr_1_4?dchild=1&keywords=3.5mm+mono+extension&qid=1626453100&sr=8-4.
After connecting the robot to a headphone, it may be necessary to increase the volume using the volume buttons on the back of the robot.