DApp on http://localhost:3000/, able to connect via metamask, but not with my personal wallet

Question

I'm using https://pub.dev/packages/wallet_connect/example to connect my custom wallet to my DApp which is on React. I am running DApp from 'npm start' on http://localhost:3000/ but I get the error:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Null check operator used on a null value

on

_sessionStore = _wcClient.sessionStore;

from code: https://pub.dev/packages/wallet_connect/example

I also see below error:

Connection refused (OS Error: Connection refused, errno = 111), address = localhost, port = 52550

RPC URL: http://localhost:3000/

When I use MetaMask, it works. It is on Goerli testnet