The folding mechanism under the cup holders may not work because it may be jammed or it may be unconnected to the holder. If it is jammed and needs to be lubricated, add lubricant to the switch until it is able to be pushed up. If it has become unattached by the plastic strips connected to their holders on the carriage, reattach the plastic strips into the black plastic holders of the carriage. To replace the cup holder, check out this repair guide.
If the front or rear wheels are not spinning freely, the brakes could be locked in place or the wheels could be installed incorrectly. If the brakes are locking the rear wheels in place, unlock the brakes by pushing the brake lever upwards. If the front or rear wheels were installed incorrectly, reinstall them with either this front wheel repair guide or rear wheel repair guide.
If your device won't fold, the switches on the handlebars may be malfunctioning. The switch on the top of the cup-holder should slide to the left. Simultaneously, the switch on the bottom of the cup-holder should be pushed up in order to unlock the device and fold it. To replace the cup-holder completely, follow this repair guide.