My WEB3 is connected to the MPPT solar controller with an RS485 serial cable but the current readings are all zero on the MPPT display and in the WEB3 MPPT page

The ground between the V- load output on the MPPT solar controller and the TPDIN-Monitor-WEB3 V- needs to be isolated for the MPPT controller to sense the currents properly.

A TP-DCDC-1224 DCDC converter can be used to isolate the power and solve this issue.