Problems reading a file and then writing it in another file - c

Question

So basically this is the code i have to read one file and then encrypt it to another one. The problem i have is that doesn't write anything in the file. Im posting just part of the code because all the code is a big block of code. I thinks its a buffer problem because it doesn't enter in the second while.
char new_array[ROWS+1][COLUMNS+1];
char frase_encriptada[160];
char frase_desencriptada[80];
void xifrar_frase(char frase[80],char matriu_x[7][7], char frase_encriptada[160]){
int i=0;
int j,k,q=0;
while(frase[i] != '\n' && frase[i] !='\0'){
for(j =1;j<=ROWS;j++){
for(k=1;k<=COLUMNS;k++){
if(frase[i] == matriu_x[j][k]){
frase_encriptada[q] = matriu_x[j][0];
q++;
frase_encriptada[q] = matriu_x[0][k];
q++;
}
}
}
i++;
}
printf("\n");
}
void xifrarArxiu(char matriu_x[7][7],char frase[80],char frase_encriptada[160])
{
FILE*fit1;
FILE*fit2;
int i;
fit1 =fopen("txtXifrat.txt","w");
fit2 = fopen("txtDesxifrat.txt","r");
if(fit1 == NULL || fit2 == NULL)
{
printf("Error al obrir un fitxer");
}
else
{
while(fgets(frase,80,fit2)!=NULL)
{
fflush(stdin);
xifrar_frase(frase,new_array,frase_encriptada);
i=0;
while(frase_encriptada[i] !='\0')
{
fprintf(fit1,"%c", frase_encriptada[i]);
i++;
}
}
feof(fit1);
fclose(fit1);
fclose(fit2);
}
}
int main(void) {
int option;
char frase[80];
char array[ROWS][COLUMNS] = {
{'A', 'B', 'C', 'D', 'E', 'F'},
{'G', 'H', 'I', 'J', 'K', 'L'},
{'M', 'N', 'O', 'P', 'Q', 'R'},
{'S', 'T', 'U', 'V', 'W', 'X'},
{'Y', 'Z', ' ', '1', '2', '3'},
{'4', '5', '6', '7', '8', '9'},
};
do
{
MenuOpcions(option);
scanf("%d",&option);
fflush(stdin);
switch (option)
{
case 3:
xifrarArxiu(new_array,frase,frase_encriptada);
break;
case 0:
printf("Sortint del programa \n");
printf("\n");
break;
default:
printf("No hi ha aquesta opcio \n");
printf("\n");
}
}while(option !=0);
return 0;
}