If your XW-MPPT is measuring almost no current or wattage (but working normally otherwise), check the negative wires. This controller must have the PV negative isolated from the battery negative.
If the negatives are connected together on a common bus, it will short out the MPPT's current shunt and keep the unit from measuring current and wattage. The unit will still function correctly, but its metering will be inaccurate or absent.
This is a notable difference from the C-series controllers, which have a common negative connection for PV and battery. Anyone who is used to wiring C-series controllers may make this mistake.
The requirement for negative wiring will be more accurately documented in the user guides in future.