The source zeroed as well

This is the circuit from the lecture, running. Change it and the answer changes with it:

• Click any component value to edit it, or drag components to rearrange.
• The wrench opens a step-by-step analysis — it chooses a reference node and writes the node equations. Leave its Domain on the DC operating point for this deck.
• The crosshairs probe reads a node voltage or a branch current, so you can check any intermediate result rather than only the final answer.

Nothing drives this, so every voltage reads zero — correctly. It is here to be looked at, not solved: $R_{Th}$ is what you get by combining what is left, $6\text{k}\|6\text{k} + 2\text{k}$.