I was having the same issue.
Try this method below to see if it works. It worked for me. I got this information through the QBO Assistant when you click on the help button on your account.
Adding your accountant is easy within Quickbooks Online!
1. Select the Settings icon then Manage Users.
2. Select Add User and Company admin.
3. Check This user is my accountant. Note: This step doesn't apply to Simple Start subscriptions.
4. Select Next.
5. Enter the accountant's name and email address, then Save.
An invitation email will be sent to your accountant.
Note: Your accountant must accept the email invitation within 24 hours, and follow the steps provided in the email to access your QuickBooks file.
