I have been cleaning and detailing my uncles boat for him in preparation for selling it. The boat starts fine but none of the switches on the dash, including the horn, seem to be working. I really don't know how to troubleshoot this correctly. I checked the fuse coming directly off the positive terminal and it is fine. The buss switch, off the negative terminal, with red button reset has been tested and it is fine (I have the black bar pushed up also). Under the driver seat area I have checked the fuse/switches and am unsure how to tell if these have been tripped. The white button setup is new to me.

Can anyone help me troubleshoot this problem?

Thanks