This means the internal enabled/disabled state of the printer, as tracked by isPaused in plasmoid/package/contents/ui/PrinterItem.qml and used to control the state of the play/pause button and the opacity of the printer name. If the printer state is changed by some external action, e.g. CUPS detecting a printer problem or the cupsenable/cupsdisable commands being used, the applet does not notice the change and still retains the previous state.
This change watches for state changes from the PrinterModel and updates the internal state (and therefore the GUI) appropriately. It could be more selective, but I've tried to guard against spurious property changes (so hopefully signals and redrawing) by only changing the isPaused property if necessary.