Where to find birth certificates?

I've been looking for birth certificates for my grandfather and some of his siblings, all born in Wellsville, but I've not been able to get any. I've contacted the county for my grandfather and his elder brother (born before Dec 1908) and the state for a younger sister (b 1912 and died two weeks later) but I always am told there are no records. I found a death certificate online for the sister and thought that requesting the birth certificate would give me new information that might help with the others.

I've tried calling the probate court and talking to them on the phone but they were still unable to help. I suppose I could try additional siblings, but of five children born in Ohio I've sent requests for three and not gotten anything. Is there somewhere else I'm supposed to be looking? Everything I've seen online says I'm talking to the right people. I can't exactly drive over there to see what is going on.

Suggestions?

Andrea Longo
San Francisco