VC2075: responsive-class-set <target>s aren't valid

A responsive-class-set's <target>s aren't valid: it has none, a target has no <option>s, two targets have the same name, or a name can't be used.

How to fix

Give the parameter a <target name="..."> for each breakpoint, each holding its <option value="class">Label</option>s, with names made of letters, digits and dashes. See Responsive classes.