Error in the Caesars Cipher exercise

I have a problem because according to me, the results that my algorithm returns are good, however it does not pass the test. Please help me!

``````  **Your code so far**
``````
``````
function rot13(str) {

let letters = {
"A": "N",
"B": "O",
"C": "P",
"D": "Q",
"E": "R",
"F": "S",
"G": "T",
"H": "U",
"I": "V",
"J": "W",
"K": "X",
"L": "Y",
"M": "Z",
"N": "A",
"O": "B",
"P": "C",
"Q": "D",
"R": "E",
"S": "F",
"T": "G",
"U": "H",
"V": "I",
"W": "J",
"X": "K",
"Y": "L",
"Z": "M",
}

let result = "";

let regexPunctuation = /\W/;

let separate = str.split(" ");

for(let i = 0; i < separate.length; i++){

for(let j = 0; j < separate[i].length; j++){

// console.log(separate[i][j])
//si on tombe sur un caractĂ¨re diffĂ©rent d'une lettre, on l'ajoute Ă  result
if(regexPunctuation.test(separate[i][j])){

result += separate[i][j];

}

else{

// console.log(letters[separate[i][j]])
result += letters[separate[i][j]];

};

}; //second boucle end

result += " ";

}; //first boucle end

console.log(result);
return result;

};

rot13("SERR PBQR PNZC");
rot13("SERR CVMMN!");
rot13("GUR DHVPX OEBJA SBK WHZCF BIRE GUR YNML QBT.")
rot13("SERR YBIR?")
``````
``````  **Your browser information:**
``````

User Agent is: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.107 Safari/537.36`

Challenge: Caesars Cipher