OK, if the wiring looks good then my next step would be to take a resistance reading of the heat-tube.
1.Remove power from the printer via the power switch or to be sure remove the power cord.
Depress the locking tab on the heater connection and remove from the hotend electronics PCB.
Insert jumper wires; use standard breadboard jumper wires and insert into each terminal of the connector. It will be snug and should not come out of the connector female terminal.
Attach a digital multimeter (DMM) in the resistance or Ohm setting with one test lead on each jumper wire inserted into the heater connector.
Reference attached pictures for measurement setup.
The OEM heater should be approximately 4.4 - 4.6 Ohms. Should it be much higher or lower then consider replacing the heater.
The OEM heater is 35 watts; a safe replacement is the E3D 12V 30 watt heater. Going higher than 35 watts may cause the controller board MOSFET transistor and/or the surface mount fuse to blow. That is not an easy repair to complete without removing the controller board from the printer.
E3D heater sources:
Amazon - http://bit.ly/E3D12V30WAMAZON
E3D - https://bit.ly/3boWxo3