Usually not. A documented system with a recent low result answers the radon question before a buyer asks it. Ohio's disclosure form asks sellers about known radon and any mitigation, so paperwork showing the problem was fixed helps.
More detail
Buyers and their inspectors look for evidence. Ohio's standards require a closeout package with the floor plan drawing, pre- and post-mitigation test data, contracts and warranties, a system description, and the installer's license number, and the drawing has to be available to future owners on request. A system with a marked gauge, a working monitor, labeled pipe, and a fan outside the living space reads as compliant at a glance. Trouble starts when a system cannot be documented or visibly misses the standard, such as a fan hanging in the basement or a discharge low on the wall beside a window. If a sale is likely in the next year, retest now so the number is fresh. See radon in a Columbus home sale.