To start, let's make sure you access the correct account by signing in to QuickBooks Online using the right login. If you don't have multiple accounts or if you used the correct sign-in info, this vendor may be invited to enter their tax info. This feature allows your vendor to add their 1099 tax info in their own account and securely share their information with you. However, they don't have the view or access to your company.
Meanwhile, I've included some articles you can use to manage user roles in QuickBooks Online: