I've been #slowcooking my split peas for a total of 24 hours and they're still hard. #AnySuggestions They soaked for 48hrs.
If they've been immersed in liquid that long and not softened, it's possible you've been sold a bag of aquarium gravel. Any dried bean or pea should be well on their way to softening up by 36 hours, and really, split peas are one of the fasted cooking dried legumes and should rarely need soaking. I'd chuck out what you have, maybe reserve cooking liquid, and start again.
I feel for you; I've had this happen with split peas too. You probably have old split peas, and they'll never really soften. Dried beans are sometimes YEARS old when they're sold, so unfortunately how long ago you bought them is only a partial indicator of their age.
This has happened to me so many times, even after only shopping at stores I know have a good product turnover. I finally gave up and only use dried beans,etc from Rancho Gordo. They cost a bit more, but always give good results