When a score is read as zero to zero or 15 to 15 it is called a

love-love or just love

Explanation:

here why from a article i read before

At the beginning of the game, when both sides have no score, the game is love-love because in tennis, love means having a score of zero or nil. One point brings a player to 15, two to 30; and three to 40. The next point wins the game, unless a complex series of tiebreakers comes into play, because in order to win a tennis match, a player must win by a margin of two.

Where did the game gets its affectionate score for zero? The Oxford English Dictionary suggests that the term might be rooted in the colloquial phrase “for love,” meaning “without stakes being wagered.” This theory reflects the sport’s long history of etiquette and sportsmanship. Others theorize that love arose from the French word for “egg,” l’oeuf, because a zero on a scoreboard resembles an egg. This is a clever claim, but it remains unsubstantiated.