I'm in the Bay Area. I have a bed where these are quite happy and reseed or reappear every year. It is a sunny spot, but by no means sunny all day long. The variety is just the regular pink echinacea...there are many new introductions with different flower type and color, but mine have got to be 10 years old or so and I have never had a need to buy more. I let them go to seed and then in the early Spring the old stalks pull right out. I then spread compost in that bed. Coneflowers do need regular water...maybe once a week...more in a heat wave. This is what works for me. I believe the first flower has just appeared.

Ditto deep roots. I had to go out in the yard to read the tag on mine ...echinacea purpurea .... planted in west-facing yard with adequate water. Planted last year and the return/reseeded growth is beautiful this year.[just OK last year] Just now starting to bloom. I will probably have to move the clump in a year or two, as a young Mullberry will soon shade that bed, and I note that they are not happy in shade. I grew some from seed in anothr location, meaning to transplant to less-watered parts of yard. Haven't done that yet. These flowers fit the 'wild woodsy' look that I like in my yard.

Here is a link that might be useful: Echinacea Purpurea

I have never had E. purpurea last for more than 2 years in several attampts, and I have never gotten any volunteer seedlings either, I am in the SF bay area. To be a true perennial I think it needs more chill hours.

Mine have never lasted more than two years either, but I've always thought my heavy clay soil was at fault. Mine never bloom more than once a year, although they are in bloom for almost two months. Never have had them rebloom in the fall. I don't think they're worth the effort. And I have no idea why anyone would want a yellow or orange Echinacea plant, when Rubeckias are almost the same thing, bloom a lot longer, and come back for several years before dying out.

OK .... mine are on the 2nd year.... but tons of seedlings around them, so think this clump will last quite a while. Hope so, anyway. These make great, long-lasting picking flowers.

I don't think that chill hours are a factor ... tho that seems logical considering the areas they are native to. But though I'm inland SD county and get a bit of chill ... have avocados and cherimoyas in my yard, so no chill here.
But may be that the micro climate where you planted yours wasn't just right. Might try a different part of the garden?