Hi there, Lucia. To make sure we're looking in the right place, could you clarify where your client is currently checking? For example, are they looking under the Gear icon or the All apps menu, and what exactly do they see on their screen?
In the Sole Trader Plus plan, the option to add an accountant is located by clicking the Gear icon > Manage users > Accounting Firms tab. Alternatively, your client can use this link to go directly to the user settings page: https://qbo.intuit.com/app/usermgt/accountants.
Also, please make sure your client is using the correct link: qbo.intuit.com. If they try to log in through the Self-Employed site with Sole Trader Plus credentials, it can cause a "phantom page" where options do not appear.
If you have other questions about the program, please don't hesitate to click the Reply button below.