You need to contact a probate attorney in the state where your grandmother died or owned land or where there estate was otherwise started in probate to at minimum review the documents to determine what procedural action to take. In many jurisdictions you have a set period of time to settle an estate and the court supervises the process. In others, the court does not step in unless someone files a petition alleging that the executor will not account for the funds or distribute or other action needs to be taken. The only way to tell is to have an attorney in the state review the documents and advise you as to procedural steps once the files have been reviewed and costs and fees to litigate the matters.
As I see it, you have two options if the named executor's non-responsive:
1. You can hire a Florida attorney to ascertain whether the estate's opened and has counsel, and to do what's appropriate to either get the executor going or get a new executor who will perform. (Under Florida law, you can very likely act as executor as a grandchild.)
2. Your less-expensive alternative is to file a caveat with the appropriate Florida court. This will require either a Florida attorney or an agent living in Florida, and the caveat ensures that the will will not be admitted to probate without you being cited as an interested person in the estate. Basically, this will help you keep tabs on the estate if it is not yet open. It'll also ensure your ability to participate in the Florida probate proceeding.
I am licensed in New York only. My answers are generally based on New York law or common law, except where otherwise indicated, and other states may make exceptions or have peculiarities resulting in different answers from an attorney licensed in the other state.