なかなか~ない (not easily)

The adverb + negative combination なかなか~ない, 'not easily / can't manage to X / X won't happen readily / just won't.' Signals frustration or stubborn resistance to a desired outcome. Without negation, なかなか is a positive intensifier ('quite, considerably'); with a negative it expresses persistent failure to do or happen — なかなか来ない ('still hasn't come'), なかなか覚えられない ('just can't memorize').