Thanks for writing! You should be able to grow cyclamen -- I grow them here in Zone 5 Iowa!
I planted mine 3 or 4 inches deep in enriched soil. These plants really like organic matter, so I added a lot of compost to the ground when I planted them.
They do best in a shady spot, too, and one where the soil drains well. So if you have lots of clay, maybe the plants were rotting? I grow most of mine in a dry corner that doesn't get any extra water --- they seem to do better here for me than in spots where I do more watering in the summer.
The two hardiest types are Cyclamen coum and Cyclamen hederifolium. The big, showy cyclamen you see at the grocery store, florist, and such aren't hardy for our area. So that's probably the problem if you were trying to grow those.
Good luck. I hope this helps!
---Justin, Senior Garden Editor, BHG.com