Simple Upgradeable Token Swap Contract Working fine on Goerli but giving errors on Eth Mainnet

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1

The upgradeable smart contract of token swap is working fine on Goerli, I can swap the tokens by calling "BuyTokens". But when I deployed the same contract on mainnet, the "buyToken" pops the error
Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
execution reverted

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/security/ReentrancyGuardUpgradeable.sol";

contract SwapERC20 is Initializable, OwnableUpgradeable, UUPSUpgradeable, ReentrancyGuardUpgradeable {

  ERC20Upgradeable public paymentToken;
  ERC20Upgradeable public contractToken;
  // token price for PTN
  uint256 private tokensPerPTN;

  // Event that log buy operation
  event BuyTokens(address buyer, uint256 amountOfPTN, uint256 amountOfTokens);
  event WithdrawTokens(address receiver, uint256 amountOfTokens);
  event NewTokenPrice(uint256 newPrice);


    function initialize(ERC20Upgradeable _paymentToken, ERC20Upgradeable _contractToken) initializer public {
        __Ownable_init();
        __UUPSUpgradeable_init();
        __ReentrancyGuard_init();
         paymentToken = _paymentToken;
         contractToken = _contractToken;
    }

  /**
  * @notice Allow users to buy token for PTN
  *///enter amount of tokens you want to buy in wei

  /**
  * @notice Allow users to buy token for PTN
  */
  function buyTokens(uint256 amount) external nonReentrant {
    require(amount > 0, "Send payment tokens to buy some tokens");
    
    uint8 contractTokenDecimals = contractToken.decimals();
    uint256 totalPaymentAmount = (amount * tokensPerPTN) / (10 ** contractTokenDecimals);
    require(totalPaymentAmount > 0, "Insufficient Payment Amount");

    // check if the Contract has enough amount of tokens for the transaction
    uint256 vendorBalance = contractToken.balanceOf(address(this));
    require(vendorBalance >= amount, "Vendor contract has not enough tokens in its balance");

    (bool received) = paymentToken.transferFrom(msg.sender, owner(), totalPaymentAmount);
    if(received) {
        // Transfer token to the msg.sender
        (bool sent) = contractToken.transfer(msg.sender, amount);
        require(sent, "Failed to transfer token to user");
    } else {
        revert("Failed to transfer tokens from user");
    }

    // emit the event
    emit BuyTokens(msg.sender, totalPaymentAmount, amount);
  }

 // enter without decimal e.g. 1 for 1 token
  function setSwapPrice(uint256 newPrice) external onlyOwner {
      require(newPrice > 0, "Price cannot be zero");
      tokensPerPTN = newPrice;

      emit NewTokenPrice(newPrice);
  }

  function getSwapPrice() external view returns(uint256) {
      return tokensPerPTN;
  }

  /**
  * @notice Allow the owner of the contract to withdraw PTN
  */
  function withdraw(uint256 amount) public onlyOwner nonReentrant {
    uint256 contractBalance = contractToken.balanceOf(address(this));
    require(amount <= contractBalance, "Owner has not balance to withdraw");

    (bool sent) = contractToken.transfer(owner(), amount);
    require(sent, "Failed to transfer token to user");

    emit WithdrawTokens(msg.sender, amount);
  }

    //uups upgradable
     function _authorizeUpgrade(address newImplementation)
        internal
        onlyOwner
        override
    {}
}

I tried to search about this issue but didn't find any helpful resources.

Goerli Contract which was used for testing: https://goerli.etherscan.io/address/0xb9e792a60b800816228f274c83f99bc181f20ca0

Mainnet Contract: https://etherscan.io/address/0x6157F9a3FC3cD5c64Ec02E093Ad4339500e49f3D

2

The function is complex so it's most likely that the error is not due to upgrades.