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The recovery process is written for people who were Costa Rican by birth, and the Tribunal Supremo de Elecciones says plainly that a former Costa Rican by naturalisation has to make a fresh naturalisation application instead. That is the same route as anyone else’s: seven years of official residence, or five if you are a national of another Central American country, Spain or an Ibero-American country by birth, plus means of living, good conduct and the Ministry of Education’s Spanish and history exams. Whether your earlier years of residence can be counted again is not something we could establish from any published source, and it is the question worth putting to the Seccion de Opciones y Naturalizaciones before you plan around a seven-year wait. One thing to check first: if the loss was recorded after 6 June 1995, when Article 16 was reformed so that the status can no longer be lost, ask them to confirm it was lawfully recorded at all.