The C++ Vigener cipher does not encrypt arrays as it should

I'm starting to learn the pros and I can't cope with the task for the vigener cipher. The function works, but it doesn't encrypt properly. String and vector are not allowed

#include <iostream>   // For Input and Output
#include <fstream>    // For file input and output
#include <string.h>
using namespace std;

const int wordLength = 81;
            
void encodeText(char text[wordLength], char key[wordLength]){
     int textLen = strlen(text);
     int keyLen = strlen(key);
     int i, j;
            
     char newKey[textLen];
     char encryptedText[textLen];
            
     //новый ключ
     for(i = 0, j = 0; i < textLen; ++i, ++j){
         if(j == keyLen){
            j = 0;
         }
         newKey[i] = key[j];
     }
     newKey[i] = '\0';
            
     //шифровка
     for(i = 0; i < textLen; i++){
         if (text[i] != ' '){
            encryptedText[i] = ((text[i] + newKey[i]) % 26);
            encryptedText[i] += 'a';
         }
         else{
            encryptedText[i] = ' ';
         }
      }
      encryptedText[i] = '\0';
            
      cout << newKey << endl;
      cout << text << endl;
      cout << encryptedText << endl;
}
        
        
int main(){
   cout << "Введи текст для шифрования: ";
   char textToEncode[wordLength];
   cin.getline(textToEncode, wordLength);
        
   cout << "Введи ключ: ";
   char keyword[wordLength];
   cin.getline(keyword,wordLength );

   cout << "Ключ, текст и шифр:  \n";
   encodeText(textToEncode, keyword);

return 0;
}
        
       

For example, the code outputs:

Введи текст для шифрования: all generalizations are false
Введи ключ: secret
Ключ, текст и шифр:  
secretsecretsecretsecretsecre
all generalizations are false
ebz wjrufdbndqhlesw ouu jqzvu
 

The code should output:

secretsecretsecretsecretsecre
all generalizations are false
spn kxfitrpbrevzsgk cii xenji