Folding bike display not working:

There is a trick of the battery lock to keep power consumption. That's the reason why the battery can't power up the bike.
Please check the video:

Keep the key at the third position that the key can't be pulled out, then press the lightning button remote fob to unlock the bike. The power will be connected after that. So if you're not using the battery, you could take out the key.
That will avoid power consumption and lower down the risk of being stolen.
Also, here are the functions of the key fob:
"Lock" refers to lock the power supply, the bike can not be turned on after pressing this button. If the power supply is locked but the bike was moved or touched, the alarm will work and make sounds. At this time, use "Unlock“ to mute the alarm.
”Lightning“ refers to unlock the power supply, the bike can be supplied with electric power after pressing this button.

Motor not working: The wheel only make a noise while pressing throttle in PAS1~3 level--Motor Troubleshooting/Motor Hall Checking

Possible causes:

  • Motor cable loose/damaged
  • Poor connection of controller
  • Clutch failure
  • E24 Hall motor

Battery not working: The battery doesn‘t charge--Battery Troubleshooting/Battery Voltage Testing

Possible causes:

  • Wrong charger/charger failure
  • Battery failure

Error code:(The motor will not work as long as the code appears)

E22=Throttle Abnormality:Screen shows E022 and the throttle is not working.--X5X7 Controller Checking/Mountain bike Controller Checking

Possible causes:

  • Throttle wire failure
  • Poor contact of controller lead

--Unplug the throttle cable connector and reconnect it. 
--Check the controller connection.

E24=Motor Hall Signial Abnormality--Motor Troubleshooting/E24Troubleshooting

Possible causes:

  • Motor cable loose/damaged
  • E24 Hall motor
  • Poor connection of controller

--Check whether the motor cable is loose or damaged.
--Refer to the testing file and use mutimeter to check the motor.

E25=Brake Abnormality:Screen shows E025, the throttle and PAS are not working--E25Troubleshooting

Possible causes:

  • Poor contact of brake lead

--Unplug the brake cable connector and reconnect it in turns.

E30=Communication Abnormality--E30Troubleshooting

Possible causes:

  • Wire faulty or poor connection