ok, looks to me like you should have wires from the wall plug going into Terminal Block 1 (TB1)

Your hot wire goes into the terminal labeled 120

Your neutral wire goes into the terminal AC Com

Now the power strip or whatever goes to your heat source appears to have the hot wire connected to the TB2 ON terminal on the right side

The neutral looks like it doubles up in the TB1 AC Com terminal

looks like there is a jumper between 120 terminal on TB1 and the C terminal on TB2