I am unable to get result showing uncaught in promise

Moralis General
#1 
const ERC20_ABI2 = [
{
constant: true,
inputs: [{ internalType: "address", name: "who", type: "address" }],
name: "customStakingBalance",
outputs: [{ internalType: "uint256", name: "", type: "uint256" }],
payable: false,
stateMutability: "view",
type: "function",
},
];
async function tsuply() {
let res = await Moralis.Web3API.native.runContractFunction({
chain: "mumbai",
address: "0xf8aDc852F8CaE4395d03AaBF5534051Bf4AEFAD1",
function_name: "customStakingBalance",
abi: ERC20_ABI2,
params: { who: currentuser },
});
console.log(res);
document.getElementById("res").innerHTML=res;

}
tsuply();

please explain me the error

#2

the syntax seems correct for Moralis.Web3API.native.runContractFunction, check the value of this parameter

#3

no i am getting user ethaddress and want to use it here can u provide me the preformated code to explain and correct this

#4

try to do some debugging, to see what it the value for that variable named currentuser