The block you dragged in is from a different library which doesn't connect directly to Simscape Power Systems Specialized Technology. Looks like you're using an older release of MATLAB, but in newer versions they've tried to make this clearer.
What you'll have to do is create a custom resistor using a current sensor and a voltage source, so that you yourself implement the lawV = I*R(t), whereR(t) can be a time-varying input signal.
Note that you'll need to break the algebraic loop with some low-pass filter as shown below.
I had the same problem and I could solve it add a block name it SIMSCAPE INTERFACE ELEMENT and SIMULINK-PS CONVERTER to convert the signal physical to a signal and use sensors of corrent-voltage. These blocks you can found in SIMSCAPE library-FOUNDATION LINRARY-ELECTRICAL