Can't get heaters to work on my new 55 gallon tank? Even though they're name-brand and proper wattaged?

I use marineland stealth pro on both of my 20 gallon tanks. I recently had to completely re-do my 20long and when i set everything back up the marineland 100watt heater raised my temp 20 degrees in less than 10 hours. I'd say you just have bad luck with heaters.