metamask balance issue

Faucet.sol

pragma solidity ^0.4.18;

contract Faucet {

    address public owner;
    address public owner2;
    
    bool public available;
    mapping (address => bool) fundedAccounts;
    
    modifier onlyOwner() {
        if(msg.sender != owner)
            revert("Only owner can change availability");
        _;
    }
    
    modifier duringAvailable() {
        if(!available)
            revert("Contract not ready to send ether");
        _;
    }
    
    constructor() public payable {
        owner = msg.sender;
        available = false;
    }
    
    function updateAvailable() onlyOwner public {
        available = !available;
    }

    function fundAccount(address _reciever) duringAvailable public payable {
        require(fundedAccounts[_reciever] == false);
        fundedAccounts[_reciever] = true;
        _reciever.transfer(0.5 ether);
    }
    
}

geth version used by my nodes

Geth/nodo maquina 1/v1.8.6-stable-12683fec/linux-amd64/go1.10"