Truffle smart contract error -32000 for working contract

Question

I have a javascript backend that I use to provide an API, which can be used to save and get strings from the blockchain.

I used truffle to deploy my contract on the Goerli test net.

And the contract is written in solidity as below:

contract StringStorage {
mapping(uint256 => string) public stringList;
uint256 public stringCount = 0 ;

function storeString(string memory _value) public {
    stringCount++;
    stringList[stringCount] = _value;
}

function getString(uint256 _index) public view returns (string memory) {
    require(_index > 0 && _index <= stringCount, "Invalid index");
    return stringList[_index];
}

function getCount() public view returns (uint256) {
        return stringCount;
    }
}

I created a script, that i used to test the deployed contract and I am able to save aswell as read strings from the blockchain. This is the script:

const Web3 = require('web3');
const contract = require('./BackendITProjektNODEJS/blockchain_setup/build/contracts/StringStorage.json');

const HDWalletProvider = require('./BackendITProjektNODEJS/blockchain_setup/node_modules/@truffle/hdwallet-provider');

const web3 = new Web3(new HDWalletProvider('myKey', 'https://rpc.ankr.com/eth_goerli')); // Replace with your Ethereum node URL

const contractAddress = 'myAdress'; // Use the address deployed by truffle migrate
const instance = new web3.eth.Contract(contract.abi, contractAddress);

async function storeString(stringToStore) {
    const accounts = await web3.eth.getAccounts();
    console.log(accounts)
    await instance.methods.storeString(stringToStore).send({ from: accounts[0] }).then((receipt) => {
        console.log('Transaction receipt:', receipt);
    })
    .catch((error) => {
        console.error('Error:', error);
    });
    console.log(`String "${stringToStore}" stored on the blockchain.`);
}

async function getString(index) {
    const storedString = await instance.methods.getString(index).call();
    console.log(`Retrieved string at index ${index} from the blockchain: ${storedString}`);
}

// Example usage:
storeString("test123");
//storeString("String 2");

//console.log(getString(3)); // Retrieve the first string
//getString(2); // Retrieve the second string

This works perfectly fine.

Now I have similiar code in my backend and I am able to call the read function and read the strings I wrote with the above script. But the StoreString function never gets executed successfully. This is the code:

import StringStorage from '../blockchain_setup/build/contracts/StringStorage.json' assert { type: "json" };
import HDWalletProvider from '../blockchain_setup/node_modules/@truffle/hdwallet-provider/dist/index.js'

import {Web3} from "web3"
class BspChain {

    constructor(){

        
        this.contract = StringStorage
      
        
        
        this.web3 = new Web3(new HDWalletProvider('myKey', 'https://rpc.ankr.com/eth_goerli'));

        
       
        this.contractAddress = 'myAdress';
       
        this.instance = new this.web3.eth.Contract(this.contract.abi, this.contractAddress);
    }

    async storeString(stringToStore) {
        console.log(stringToStore)
        
        const accounts = await this.web3.eth.getAccounts();
      
        //await instance.methods.storeString(stringToStore).send({ from: accounts[0] });
        await this.instance.methods.storeString(stringToStore).send({ from: accounts[0] })
        .then((receipt) => {
            console.log('Transaction receipt:', receipt);
        })
        .catch((error) => {
            console.error('Error:', error);
        });
    
       
    }
    
    async getString(index) {
        //const storedString = await instance.methods.getString(index).call();
        const storedString = await this.instance.methods.getString(index).call();
        console.log(`Retrieved string at index ${index} from the blockchain: ${storedString}`);
        return storedString
    }

}

export { BspChain as default };

I am catching the following error:

Error: {
  jsonrpc: '2.0',
  id: 'e056ced5-bea4-4dc2-8663-2a57e5f0a967', //this naturally changes each try 
  error: { code: -32000, message: 'execution reverted' }
}

I am somewhat clueless.

Please notice I changed personal information.

I appreciate every hint and help I get.

Many Thanks in advance.