Hi Karen,
The error is pointing to the Voltmeter IV1 and the switch control Model1, looks like one is Positive and the other is OFF.
Please carefully check the setup of these components. I would suggest checking the characteristics of each one, to do this in the Properties window of each component you can find a direct link to Help.
Note: check also the component IV2 because probably you have the same setting mistake.
Ivonne
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