21H Voltage Current Error
The battery is not supplying the required voltage to power the display and motor. This can be caused by working the internal controller, motor, and/or battery too hard in some cases (long extended climbs with the rider not pedaling hard enough).
22H Throttle Error
When you press and release the throttle, it should return to its original position. Remove any obstructions. Check the throttle and throttle cable for damage, such as a cut, frayed cable, or loose
connection point.
23 Motor Phase Error and

24 Motor Communication or Hall Sensor Error
Check the motor cable connection point by the chainstay. Check the cable connection, disconnect it carefully, and make sure it is free from grit or contaminants, properly aligned, and firmly connected. This error might appear if you don’t reconnect the cable after removing the rear wheel (for example, after changing a flat tire or transporting your bike in or on your vehicle). At least one of the motor phase wires has been damaged or is temporarily disconnected. Another possible cause is damage to the motor cable as it exits the axle, perhaps if the wheel was dropped on the cable or something hit or pulled the cable. Check the motor cable connection point by the chainstay. Check the cable connection, disconnect it carefully, and make sure it is free from grit or contaminants, properly aligned, and firmly connected. This error might appear if you don’t reconnect the cable after removing the rear wheel (for example, after changing a flat tire or transporting your bike in or on your vehicle). At least one of the motor phase wires has been damaged or is temporarily disconnected. Another possible cause is damage to the motor cable as it exits the axle, perhaps if the wheel was dropped on the cable or something hit or pulled the cable.

25H EBS (Electronic Brake Shutoff)
Disconnect the electronic brake shut-off wire one at a time to determine if it is caused by one or both. This can often happen after a crash or when the bike is dropped. Could you look at both levers for signs of damage or the lever not returning to the proper position?

26H Low voltage protection 

26H indicates that the measured voltage is below the low voltage protection setting on display. To resolve this problem, it is recommended to decrease the low voltage protection setting. To do this, go to advanced settings, select Low voltage protection, and set it to 48V. Then, adjust the voltage to a lower number between 37V and 39V.

30H Communication Error
A problem with the connection from the internal controller to the display. The display needs to receive vital information. Often the issue is a stressed or damaged display cable; however, it can be related to the internal controller and, in rare instances, the motor.