My advice is never give up!
It took years to find my ggrggrandmother on one particular census.
In fact, she had re-married when quite old and though her some of her children were resident with her, their surname had been mis-spelled, so didn' tcome up in on-line searches.
Given that the family never moved out of one small neighbourhood, I'd have had quicker results by just going over all the pages of census returns for the area, I think.