Of course the prosecutor is going to say that. He/she would be who represents the Sheriff in an appeal. And they are not doing what Ohio law says. Expungement is one of the exceptions listed in the procedures for the Sheriff to follow when issuing a CHL, but that section also lists record sealing, restoration by court order and by operation of law. If Florida restores firearms rights to those adjudicated as being delinquent for a disqualifying offense when the person turns 24, then the Sheriff is required to issue the CHL.
You will probably have to hire an attorney to get this resolved. While an attorney may not already be aware of the legal requirements, he/she should be able to understand it if you print copies of the laws I provided links to and give them to him/her. Just tell the lawyer that the law recently changed.
Pretty much any other state, you would be up a creek without a paddle--even with a pardon. Virginia just changed their laws to accept other states' restorations. Montana does and Alaska would work simply due to the lack of prohibition laws. I am not aware of any other state besides Ohio.
What is funny is that most states have reciprocity agreements with other state's to recognize CHL licenses, but they don't recognize each other's restorations. So you could have a CHL from Ohio that is recognized by Texas, but if you ever lost your rights and had them restored, Texas would lock you up for a felony for possessing the firearm. But Ohio recognizes a Texas CHL and a Texas restoration. This situation exists because people (i.e., most politicians and lawyers and LE) don't understand firearms restoration law.
"Laws that forbid the carrying of arms**disarm only those who [don't] commit crimes. Such laws make things worse for the assaulted and better for the assailants; they serve rather to encourage than prevent homicides." - Thomas Jefferson.