I'll ensure your client can integrate the Wix Connector app, Suzanne.

It's important to note that only the Primary and Company admin can add apps in QuickBooks. If your client lacks the necessary permissions, you can change their role to company admin so they can add the app themselves.

Here's how:

1. Sign in to your client's account as the primary admin.
2. Go to Settings and select Manage users.
   
3. Locate your client's name and click Edit.
   
4. From the Roles dropdown, choose Company admin.
   
5. Select Save changes.

Once done, refer to this article for the detailed steps in integrating Wix with QuickBooks Online using QB Connector: Integrate QBO with Wix using OneSaas.

I've added this resource to guide you about usage limits in QuickBooks Online: Maximum number of accounts or users.

If you have additional questions, feel free to comment below.