WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
You clicked the nodes when running a .op (dc operating point) run on the sim. When you close reopen the sim those points will be question marks and change to the voltages when you re-run it.