Overview
HubSpot allows you to register a custom app via OAuth authentication by entering your ID/Password, but
You need to add permission to connect apps in HubSpot.
*Note: Only users with "super administrator rights" can add permissions.
Steps to Add Permissions
Please log in to HubSpot and select the gear icon in the top-right corner.
Please select "Users & Teams" in the sidebar.
Select "Actions" for the relevant user and choose "Make Super Admin".
Log in to Yoom, register your custom app for HubSpot,
and confirm that you can register your custom app without any issues.
This completes the custom app registration in HubSpot 🎉