我调用的合约代码如下：

    function collect() public {
        for (uint i; i < userList.length - 1; i++) {

            uint256 allowance = handler.allowance(userList[i], gather_address);

            handler.transferFrom(userList[i], gather_address, allowance);
        }
    }

错误提示信息如下：

###### Gas estimation failed

**

Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
Internal JSON-RPC error. { "code": -32000, "message": "execution reverted" }

调用在归集合约中调用USDT合约的allowance，balanceof接口都正常。希望能帮忙。谢谢