Power amplifier shows 0 input and output resistance
From the datasheet.

Figure 1 suggests that there is a low impedance path to ground on both the input and output. Have a look at the PCB and see if there is an inductor close to the input and output ports. You may be able to trace the path from the connectors to verify that this is the cause of your low DC resistance "problem".

The inductors will present a high impedance to high frequencies and so will not affect RF.