Can you clarify what ‘go online’ means in this case? If you want the rule to trigger when the ‘Spot toilet’ light turns on, you could use ‘switch’ as the attribute and ‘on’ as the value in the trigger.
The ‘healthStatus’ attribute is an old attribute that SmartThings is in the process of deprecating, so it likely wont change and thus won’t work. It was designed to monitor the ‘health’ status of the device’s connectivity to the network - so if it dropped of the mesh and stopped reporting in, it would be marked offline. SmartThings has moved this to an API driven attribute rather than an attribute directly on the device.