You are required to upgrade to the Agency Plus membership in order to be able to invite the Business Manager to your agency account. Without this membership, you will not be able to add a Business Manager, which is a required step to use GigRadar.
To subscribe to Agency Plus:
Log in to your Upwork account and switch to your agency profile.
Go to Settings > Membership & Connects.
Click the View or Edit Membership Plan.
Click the Upgrade button on the Plus plan. You should see the below summary when you successfully subscribe to the plan.
