Help with attached spa

Hey everyone, new pool and spa owner here. I'm unsure of the names of the pumps etc BC I haven't moved in yet. When inspecting the home we found two things with the attached spa. First, the black plunger looking plug was off of the ledge of the spa and I guess you press it and it pushes air to the jets or motor to activate the jets and air flow? Well, the black button was off and not sealed and being In florida we get a lot of rain and I think its clogged with water. So can I unclog that and reseal? The second question is I have a Hayward electric spa heater as well. Owner says it doesn't work, however house isn't that old and I don't think they used it much. Any indicators I can look for to see if its a breaker or what not? Any help would be appreciated! Att