I guess the ground of this verilogA block is different from analog ground. You should find which GND is the reference of it and connect the correct symbols on the testbench to each other.
I have no experience with this. I just see your post.
I recognized that none of the voltages in the schematic show the unit "V". .. just in the macro view.
Maybe it mis-interprets the "V"? can you omit the "V" to see what happens?